Control method of master-slave current sharing control system

Abstract

The invention discloses a master-slave current sharing control system, which comprises a converter master module and a plurality of slave modules which are connected in parallel, the master-slave current sharing control system further comprises a controller, an isolating circuit and a multi-stage selector. The controller compares the predicted value and the actual value of the inductive current of each circuit module in the current period, judges whether the circuit breaks down or not, and outputs a combined gating signal to the multistage selector; and according to the combined gating signal, the multi-stage selector selects an actual value of the inductive current consistent with the corresponding inductive current predicted value from the master module and each slave module in a switching period as reference data for current sharing control and sends the reference data to the controller. According to the master-slave current-sharing control system, current-sharing control can still be carried out when the master module of the master-slave structure has a switching fault, and the inductive current of a normal module can be selected in a switching period to serve as reference data of current-sharing control.

Description

Technical Field

[0001] The present invention relates to the technical field of DC-DC converters, and particularly to a control method for a master-slave current sharing control system. Background Art

[0002] In a system of parallel DC-DC converters (such as a photovoltaic power generation system, a computer room server, an electric vehicle, etc.), differences in the external characteristics of the converters (such as different line impedances, etc.) will cause the output currents of each module to vary greatly, thus affecting the stability of the system operation. Therefore, current sharing control of the system is required.

[0003] Master-slave current sharing control is a traditional solution. In this method, a master module is pre-selected among n converter modules, and the remaining n - 1 converters are set as slave modules. All slave modules will dynamically adjust according to the parameters of the master module, and finally achieve the purpose of balancing the output current. However, when a switching fault occurs in the master module, the slave modules cannot obtain reference data, and the regulation of the entire system will have problems or even break down. Therefore, corresponding control strategies are needed to meet the requirement that the master-slave current sharing control system can still operate under the condition of a switching fault in the master module. Summary of the Invention

[0004] The purpose of the present invention is to provide a master-slave current sharing control system that meets the requirement that the system can still operate under the condition of a switching fault in the master module.

[0005] The technical solution for achieving the purpose of the present invention is as follows:

[0006] A master-slave current sharing control system includes a parallel-connected converter master module and multiple slave modules; the master module and the slave modules adopt the same circuit module; the master-slave current sharing control system further includes a controller and a multi-stage selector;

[0007] The controller inputs the actual value of the inductor current of each circuit module in the current switching period, and compares it with the predicted value of the inductor current of this circuit module calculated in the current switching period, and judges whether a fault occurs in the circuit of the master-slave current sharing control system according to the difference between the predicted value of the inductor current and the actual value of the inductor current; there are multiple strobe signal lines arranged between the controller and the multi-stage selector, and a combined strobe signal is output to the multi-stage selector according to the fault situation;

[0008] The multi-stage selector is used to select, according to the combined strobe signal, an actual value of the inductor current that is consistent with the predicted value of the inductor current from the master module and each slave module within one switching period as the reference data for current sharing control and send it to the controller.

[0009] Further, the formula for the controller to predict the inductor current of the current switching period is:

[0010]

[0011] Wherein, I L (n) represents the inductor current of the current switching period, i.e., the predicted value; I L (n - 1) represents the inductor current of the previous switching period, which is the actual value of the inductor current of the previous switching period; V in is the input voltage; V o is the output voltage; D is the duty cycle of the PWM; L is the inductance value; T sw is the switching frequency.

[0012] Further, the multi - stage selector includes a plurality of cascaded two - to - one selectors, and the control terminal of each two - to - one selector is connected to a gating signal of the controller; the input terminals of the first - stage two - to - one selector respectively input the digital quantities of the actual inductor currents of the main module and the first slave module, and the input terminals of the second - stage two - to - one selector respectively input the output signal of the first - stage two - to - one selector and the digital quantity of the actual inductor current of the second slave module; and so on. The output of the last - stage two - to - one selector is connected to the controller, and sends the digital quantity of the actual inductor current of the gating circuit module to the controller.

[0013] Further, the two - to - one selector includes two logic AND gates, one logic NOT gate, and one logic OR gate; the first inputs of the two logic AND gates are respectively connected to the digital quantities of the actual inductor currents of the two circuit modules; the second inputs are respectively connected to the gating signal of the two - to - one selector and the signal obtained by inverting the gating signal through the logic NOT gate; the outputs of the two logic AND gates are the two inputs of the logic OR gate, and the output of the logic OR gate is the output of the two - to - one selector.

[0014] Further, the master - slave current sharing control system further includes an isolation circuit; the isolation circuit is arranged in the path of the inductor current input to the controller, and the isolation circuit includes a control terminal, and the control terminal is connected to the controller, and is used for sending a control signal to isolate the input of the inductor current when the controller determines that a circuit fault occurs.

[0015] Further, the isolation circuit includes a logic AND gate, and the two input terminals of the logic AND gate are respectively connected to the inductor current and the control signal P of the controller; the output terminal of the logic AND gate is connected to the controller;

[0016] When the controller detects that the main module is operating normally, that is, when the difference between the predicted value and the actual value of the inductor current does not exceed the threshold, the control signal P is set to 1; when the controller detects that the main module is abnormal, that is, when the difference between the predicted value and the actual value of the inductor current exceeds the set threshold, the control signal P is set to 0.

[0017] The master-slave current sharing control system of the present invention has the following advantages:

[0018] In this embodiment, when a switching fault occurs in the master module of the master-slave structure, current sharing control can still be performed.

[0019] In this embodiment, through methods such as logic gate circuits and CPLDs, using hardware logic control, a switching fault can be identified within one switching cycle, and the inductor current of a normal module can be selected as the reference data for current sharing control.

[0020] In this embodiment, the multi-stage selector has a sequential selection function. When the m-th circuit module serves as the master module and fails, the (m + 1)-th circuit module will be sequentially selected as the new master module for master-slave current sharing control. Brief Description of the Drawings

[0021] Figure 1 is the system block diagram of a one-master-three-slave master-slave current sharing control system related to the present invention;

[0022] Figure 2 is the control circuit of the master-slave current sharing control system of the present invention. Detailed Embodiment

[0023] To further illustrate each embodiment, the present invention provides drawings. These drawings are part of the disclosure of the present invention, mainly used to illustrate the embodiments, and can be combined with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0024] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0025] The master-slave current sharing control system includes at least one master module and one slave module. Taking the parallel BUCK circuit as an example, as Figure 1 shown, the component parameters of the four circuits are the same. Adopting the master-slave current sharing control mode, circuit ① is set as the master module, and the remaining circuits ②, ③, and ④ are slave modules. Taking the inductor current of the master module (i.e., I L1 ) as the feedback value of all circuits, the I L1 data is sampled by the current sensor and output to the controller. The duty cycles of the switching elements of each circuit (i.e., P1, P2, P3, P4) are calculated through the PID control algorithm, dynamically adjusting the conduction time of the switching elements, regulating the energy storage and release of the inductor, converting the higher input voltage into a lower output voltage, and equalizing the inductor currents in each circuit.

[0026] In this example, the relationship between the output voltage and the input voltage is as follows:

[0027] V o = P n × V in , n = 1, 2, 3, 4

[0028] In traditional master - slave current sharing control, after information such as the inductor current and output voltage of the master module are fed back to the controller for calculation and processing, a PWM wave is directly generated to control the on - off of the switching element.

[0029] As Figure 2 shown, the present invention provides an embodiment of the control circuit of a master - slave current sharing control system. In this embodiment, the models of each component are: logic AND gate SN74AHC1G08, logic OR gate SN74AHC1G32, logic NOT gate SN74LVC1G04, ADC converter ADS1110, DSP controller F280039C.

[0030] The input - output ports are set as follows: I L1 The sampled value is connected to GPIO48 via ADC1 converter, I L2 The sampled value is connected to GPIO49 via ADC2 converter, I L3 The sampled value corresponds to ADC channel A3, the sampled value of the output voltage Vo corresponds to ADC channel A4, the control signal P1 corresponds to channel EPWM1A, the control signal P2 corresponds to channel EPWM2A, the control signal P3 corresponds to channel EPWM3A, the selector input signal S1 corresponds to GPIO50, and the selector input signal S2 corresponds to GPIO51. I L1 The digital quantity output AI L1 corresponds to GPIO52, I L2 The digital quantity output AI L2 corresponds to GPIO53, I L3 The digital quantity output AI L3 corresponds to GPIO54, and the output signal sig of the selector corresponds to GPIO55.

[0031] For simplicity of description, a two - stage selector is used for the multi - stage selector of this control circuit, which can realize the gating control of one master module and two slave modules of a three - parallel BUCK converter circuit. The prediction current function is used to identify whether a switching fault occurs in the master module. When a fault occurs, the next module can be sequentially selected as the master module through the multi - stage selector, and the duty cycle is recalculated, and finally a PWM wave is generated again.

[0032] Prediction current function: Through the duty cycle D of PWM, input voltage Vin, output voltage Vo, inductance value L, switching frequency T swAnd the parameters of the inductor current in the previous switching cycle, using the formula For each circuit, calculate the inductor current I of the current switching cycle. L (n) (predicted value) and compare it with the actual measured current information. If the absolute value of the difference between the predicted value and the actual value is less than the set threshold, it is determined that the circuit is fault-free. If the absolute value of the difference between the two is greater than the threshold, it is determined that the circuit is faulty. Among them, n represents the current switching cycle; n-1 represents the previous switching cycle; when there is no need to display the switching cycle information, the inductor current is expressed as I L , the predicted current is expressed as I LP Similarly, the inductor current of the main module is expressed as I L1 , the predicted current is expressed as I LP1 .

[0033] Circuit isolation function: With the predicted current function, when the main module (i.e., circuit ①) operates normally, the difference between the measured inductor current and the predicted inductor current does not exceed the set threshold, and the controller outputs S1=1, then the logic AND gate H1 normally outputs the inductor current value through the ADC conversion module ADC1 to the controller; when the switch device of the main module (i.e., circuit ①) fails, the inductor current is abnormal, and the difference with the predicted current exceeds the set threshold, the controller outputs S1=0, then the logic AND gate H1 outputs 0, and circuit ① is isolated. Similarly, when circuit ② operates normally, the controller outputs S2=1, and the logic AND gate H2 normally outputs the inductor current value through the ADC conversion module ADC2 to the controller. When circuit ② fails, the controller outputs S2=0, and circuit ② is isolated.

[0034] Sequence selection function: When the main module has no fault, the absolute value of the difference between the inductor current and the predicted current is less than or equal to the threshold T r (|I LP1 -I L1 |≤T r ), the controller outputs S1=1, S2=1, making the selector output Finally, circuit ① is maintained as the main module, and I L1 As a reference value, current sharing control is performed; when the main module fails, the circuit ① is isolated, and the absolute value of the difference between the inductor current and the predicted current is greater than the threshold value (|I LP1 -I L1 |>T r ), the controller outputs S1 = 0, S2 = 1, so that the selector outputs This is equivalent to selecting circuit ② as the main module, with I L2 As a reference value for current sharing control. Further, when circuit ② also fails, that is, |I LP2 -I L2 |>T r, the controller outputs s1 = 0, s2 = 0, such that the selector outputs Select circuit ③ as the main module, with I L3 as the reference value for current sharing control.

[0035] In this embodiment, when a switching fault occurs in the main module of the master-slave structure, current sharing control can still be performed.

[0036] In this embodiment, through means such as logic gate circuits and CPLDs, using hardware logic control, a switching fault can be identified within one switching cycle, and the inductor current of a normal module can be selected as the reference data for current sharing control.

[0037] In this embodiment, a logic AND gate circuit is inserted at the inductor current input stage of the controller MCU, and the output of the logic AND gate circuit is converted through the fault identification function, so as to isolate the main circuit from the controller MCU when a fault occurs in the current main circuit.

[0038] In this embodiment, a two-to-one selector composed of two logic AND gate circuits, one logic NOT gate circuit, and one logic OR gate circuit is used as a unit to form a Figure 2 two-stage selector as shown. Multiple-stage selectors can be formed according to this control logic. For example, through N strobe signals, N two-to-one selectors form an N-stage selector.

[0039] In this embodiment, the multi-stage selector has a sequential selection function. When the m-th circuit module is used as the main module and a fault occurs, the (m + 1)-th circuit module will be sequentially selected as the new main module for master-slave current sharing control.

[0040] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, those skilled in the art should understand that various changes can be made to the present invention in terms of form and details without departing from the spirit and scope of the present invention defined by the appended claims, and all of them fall within the protection scope of the present invention.

Claims

1. A master-slave current sharing control system, comprising a converter master module and a plurality of slave modules connected in parallel; characterized in that: The master module and the slave module use the same circuit module; the master-slave current sharing control system also includes a controller and a multi-stage selector; The controller inputs the actual value of the inductor current of each circuit module in the current switching cycle, and compares it with the calculated predicted value of the inductor current of the circuit module in the current switching cycle, and judges whether the circuit of the master-slave current sharing control system fails according to the difference between the predicted value of the inductor current and the actual value of the inductor current; a plurality of selection signal lines are arranged between the controller and the multi-stage selector, and a combined selection signal is output to the multi-stage selector according to the fault condition; The multi-stage selector is used to select an actual inductor current value consistent with the corresponding inductor current prediction value from the main module and each slave module within a switching cycle according to the combined selection signal as reference data for current sharing control and send it to the controller.

2. The master-slave current sharing control system according to claim 1, characterized in that: The controller predicts the inductor current of the current switching cycle as follows: Among them, I L (n) represents the predicted value of the inductor current in the current switching cycle; I L (n-1) represents the actual value of the inductor current in the previous switching cycle; V in is the input voltage; V o is the output voltage; D is the duty cycle of PWM; L is the inductance value; T sw is the switching frequency.

3. The master-slave current sharing control system according to claim 1, characterized in that: The multi-stage selector includes a plurality of cascaded two-to-one selectors, wherein the control end of each two-to-one selector is connected to a selection signal of the controller; the input end of the first-stage two-to-one selector respectively inputs the digital quantities of the actual values ​​of the inductor current of the master module and the first slave module, and the input end of the second-stage two-to-one selector respectively inputs the output signal of the first-stage two-to-one selector and the digital quantity of the actual value of the inductor current of the second slave module; and so on, the output of the last-stage two-to-one selector is connected to the controller, and the digital quantity of the actual value of the inductor current of the selection circuit module is sent to the controller.

4. The master-slave current sharing control system according to claim 3, characterized in that: The two-to-one selector includes two logic AND gates, a logic NOT gate and a logic OR gate; the first inputs of the two logic AND gates are respectively connected to the digital quantities of the actual values ​​of the inductor currents of the two circuit modules; the second inputs are respectively connected to the selection signal of the two-to-one selector and the signal inverted after the selection signal passes through the logic NOT gate; the outputs of the two logic AND gates are the two inputs of the logic OR gate, and the output of the logic OR gate is the output of the two-to-one selector.

5. The master-slave current sharing control system according to claim 1, characterized in that: It also includes an isolation circuit; the isolation circuit is arranged in the path of the inductor current input to the controller, and the isolation circuit includes a control end, which is connected to the controller and is used to send a control signal to the isolation circuit to isolate the input of the inductor current when the controller determines that the circuit fails.

6. The master-slave current sharing control system according to claim 5, characterized in that: The isolation circuit includes a logic AND gate, the two input ends of the logic AND gate are respectively connected to the inductor current and the control signal P of the controller; the output end of the logic AND gate is connected to the controller; When the controller detects that the main module is operating normally, that is, the difference between the predicted value and the actual value of the inductor current does not exceed the threshold, the control signal P is set to 1; when the controller detects that the main module is abnormal, that is, the difference between the predicted value and the actual value of the inductor current exceeds the set threshold, the control signal P is set to 0.

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