A dc power spring control method and system based on dead-beat power prediction

Abstract

The application discloses a DC power spring control method and system based on a no-difference power prediction, which is used for power control of a DC power spring circuit topology. The method comprises the following steps: calculating key and non-key load power according to measured key and non-key load voltages; calculating current two-port and three-port phase shift angles according to a discrete three-port active bridge system power model prediction equation group under phase shift control by using the calculated key and non-key load power and the phase shift angles of the two-port and three-port in the last time three-port active bridge phase shift control; applying the phase shift control on the two-port and three-port full-bridge converters to realize the control of the three-port active bridge; and meanwhile, when the actual value and the reference value of the key load power deviate greatly, obtaining a PWM modulation duty ratio according to proportional integral control, applying the PWM control on a bidirectional Buck-Boost circuit to realize the control of the bidirectional Buck-Boost circuit.

Description

TECHNICAL FIELD

[0001] The application relates to a direct-current power spring control method and system based on a dead-beat power prediction, and belongs to the technical field of power electronics applications. BACKGROUND

[0002] Under the global energy shortage and the promotion of energy saving and emission reduction, distributed power generation technology has attracted much attention. However, directly connecting distributed power to the grid not only has low economic benefits, but also may interfere with the stable operation of the main grid. At the same time, due to the intermittency and unpredictability of these power sources, these power sources are usually isolated from the main grid, but this will cause resource waste, and the application of microgrids can well solve this problem. Compared with AC microgrids, DC microgrids have advantages in home scenarios because they reduce multiple power conversion modules from distributed power sources to loads, which can effectively improve efficiency and economy. In addition, in a DC microgrid, only active power is usually concerned, and the relevant voltage can be controlled, so it has attracted much attention from scholars.

[0003] The control of a DC microgrid is relatively simple and mature, and there are many implementation schemes. The main principle is to realize the control of the relevant voltage by the charge and discharge of the energy storage module, so as to ensure the stability and controllability of the microgrid. However, the frequent exchange of electric energy of the energy storage module will lead to the reduction of its service life and efficiency. In addition, the economy of large-capacity energy storage devices and the inconvenience of centralized management also have obvious disadvantages. Therefore, in a distributed DC microgrid, it is an industry hotspot to realize the energy storage module with higher efficiency, longer duration and better cost performance. The power spring is one of the solutions, which realizes the stable and efficient goal of the energy storage module and the whole system through reasonable power distribution.

[0004] At present, the control algorithm of the DC power spring has been developed, but there is still no power control strategy based on the prediction method in the aspect of power control. SUMMARY

[0005] The application solves the technical problem of providing a DC power spring control method and system based on a dead-beat power prediction, which is used for power control of a DC power spring circuit topology.

[0006] The application adopts the following technical solutions to solve the above technical problems:

[0007] A direct current power spring control method based on a dead-beat power prediction is used for power control of a direct current power spring circuit topology; the direct current power spring circuit topology comprises a direct current bus, a three-port active bridge, a key load, a non-key load, a bidirectional Buck-Boost circuit and a battery, the direct current bus is connected to one port of the three-port active bridge, the non-key load is connected to two ports of the three-port active bridge, the key load is connected to three ports of the three-port active bridge, the bidirectional Buck-Boost circuit is connected between the key load and the battery, and each port comprises a full-bridge converter;

[0008] The control method is specifically as follows:

[0009] The voltages of the key load and the non-key load in the circuit topology are measured;

[0010] According to the measured voltages of the key load and the non-key load, the power of the key load and the non-key load under a pure resistive load is calculated by using Ohm's law;

[0011] According to the calculated power of the key load and the non-key load, the power reference values of the key load and the non-key load, the phase-shifting angles of the two ports and the three ports at the last moment, and the discrete power model prediction equation set of the three-port active bridge under phase-shifting control, the phase-shifting angles of the two ports and the three ports at the current moment are calculated, the corresponding phase-shifting angles of the two ports and the three ports are applied to the full-bridge converters of the two ports and the three ports through phase-shifting control, and power control is realized;

[0012] The error is calculated by using the power reference value of the key load and the calculated power of the key load, the error is input into a proportional-integral controller, and the output of the proportional-integral controller is used as a duty cycle to generate a PWM wave; according to the size relationship between the error and the power reference value of the key load, the upper and lower bridge arm switches of the bidirectional Buck-Boost circuit are controlled.

[0013] A direct current power spring control system based on a dead-beat power prediction is used for power control of a direct current power spring circuit topology; the direct current power spring circuit topology comprises a direct current bus, a three-port active bridge, a key load, a non-key load, a bidirectional Buck-Boost circuit and a battery, the direct current bus is connected to one port of the three-port active bridge, the non-key load is connected to two ports of the three-port active bridge, the key load is connected to three ports of the three-port active bridge, the bidirectional Buck-Boost circuit is connected between the key load and the battery, and each port comprises a full-bridge converter;

[0014] The control system comprises:

[0015] A measuring module is configured to measure the voltages of the key load and the non-key load in the circuit topology;

[0016] A power calculation module is configured to calculate the key load and non-key load power under pure resistance load according to the measured key load and non-key load voltage by using Ohm's law;

[0017] A three-port active bridge control module is configured to calculate the phase-shifting angles of the two-port and three-port at the current time according to a discrete power model prediction equation group of the three-port active bridge under phase-shifting control by using the calculated key load and non-key load power, the key load and non-key load power reference values, and the phase-shifting angles of the two-port and three-port at the previous time, and to realize power control by applying the phase-shifting angles of the two-port and three-port to the full-bridge converters of the two-port and three-port through phase-shifting control.

[0018] A bidirectional Buck-Boost circuit control module is configured to calculate an error by using the key load power reference value and the calculated key load power, to input the error into a proportional-integral controller, and to generate a PWM wave by taking the output of the proportional-integral controller as a duty cycle, and to control the upper and lower bridge arm switches of the bidirectional Buck-Boost circuit according to the size relationship between the error and the key load power reference value.

[0019] Compared with the prior art, the above technical solution has the following technical effects:

[0020] 1. The control method calculates the phase-shifting angles of the two-port and three-port at the next time by using the discrete power model prediction equation group of the three-port active bridge under phase-shifting control, and applies the phase-shifting angles to the full-bridge converters of the two-port and three-port through phase-shifting control, thereby achieving the power control effect on the direct current power spring system.

[0021] 2. The control method calculates the phase-shifting angles of the two-port and three-port according to the circuit parameters and the measured values, and applies the phase-shifting angles to the full-bridge converters, which has a fast dynamic response, a simple structure, and is easy to implement, and the three-port active bridge part does not need to be controlled by the PI controller parameters. DETAILED DESCRIPTION

[0022] Figure 1 is a circuit topology structure diagram to which the control method of the application is applied;

[0023] Figure 2 is a control method flowchart of the application;

[0024] Figure 3 is a two-port and three-port power waveform in which the two-port power given value is 20W and changes to 16W at 0.1s, and the three-port power given value is 20W and changes to 24W at 0.15s. DETAILED DESCRIPTION

[0025] Embodiments of the present application are described in detail below with reference to the attached drawing figures, wherein the embodiments described are exemplary and should not be construed as limited to only the embodiments described herein. The embodiments described below are described with reference to the attached drawing figures, wherein:

[0026] As shown in Figure 1 , a DC power spring control method based on zero-error power prediction, the applied circuit topology includes: DC bus, three-port active bridge, critical load, non-critical load, bidirectional Buck-Boost circuit and battery; the non-critical load is connected to the two-port of the three-port active bridge, the critical load is connected to the three-port of the three-port active bridge, and the bidirectional Buck-Boost circuit is connected to the critical load and the battery; according to the system power model prediction equation set of the discretized three-port active bridge under phase-shift control, the reference values of the critical load and the non-critical load power are taken as the actual values of the system power at the next time, and the phase-shift angle of the current two-port and three-port is calculated.

[0027] In Figure 1 , V dc is the DC bus, C1, C2 and C3 are the voltage stabilizing capacitors of the one-port, two-port and three-port respectively, L1, L2 and L3 are the transformer leakage inductances of the one-port, two-port and three-port respectively, R2 is the non-critical load, R3 is the critical load, S2 and S1 are the upper and lower bridge arm switches of the bidirectional Buck-Boost circuit, L b is the inductance of the bidirectional Buck-Boost circuit, C b is the capacitance of the bidirectional Buck-Boost circuit, V battery is the battery.

[0028] As shown in Figure 2 , a DC power spring control method based on zero-error power prediction, comprising the following steps:

[0029] S1, measure the critical load and non-critical load voltage in the system.

[0030] S2, according to the measured critical load and non-critical load voltage, calculate the critical load and non-critical load power under pure resistive load by using Ohm's law.

[0031] S3, using the calculated critical load and non-critical load power, the reference value of the critical load and non-critical load power, the two-port and three-port phase-shift angle at the last time, and the circuit parameters, according to the discretized power equation set of the three-port active bridge under phase-shift control, calculate the phase-shift angle of the two-port and three-port at the next time, and apply the phase-shift angle to the full-bridge converter of the two-port and three-port through phase-shift control, realize power control.

[0032] The specific steps of S3 include:

[0033] S31, calculating the correction of the two-port phase-shifting angle and the correction of the three-port phase-shifting angle according to the discrete power model prediction equation group of the three-port active bridge under the phase-shifting control;

[0034] The discrete power model prediction equation group of the three-port active bridge under the phase-shifting control is as follows:

[0035]

[0036] The correction of the two-port phase-shifting angle and the correction of the three-port phase-shifting angle are as follows:

[0037]

[0038] S32, superimposing the corrections of the two-port and three-port phase-shifting angles on the two-port and three-port phase-shifting angles controlled last time respectively to obtain new two-port and three-port phase-shifting angles;

[0039] S33, if the new phase-shifting angle calculated is less than 0, setting it equal to 0, and if the phase-shifting angle is greater than π / 2, setting it equal to π / 2.

[0040] S34, delaying the control signals of the four switching tubes of the one-port full-bridge converter by the two-port and three-port phase-shifting angles respectively to obtain the control signals of the four switching tubes of the two-port and three-port full-bridge converters, wherein the control signals of the four switching tubes of the one-port full-bridge converter are fixed-frequency square waves, and the control signals of the two switching tubes of the same bridge arm are complementary, and the control signals of the two switching tubes connected to the same polarity end of the DC side are complementary.

[0041] S4, calculating the error by using the actual power of the key load and the power reference value, inputting the error into the proportional-integral controller, generating the PWM wave by taking the output of the proportional-integral controller as the duty cycle, and controlling the upper and lower bridge arms of the bidirectional Buck-Boost circuit according to the size relationship between the error and 0.01 times and -0.01 times the key load power reference value.

[0042] whether the limit is exceeded, if the limit is exceeded, inputting the error into the proportional-integral controller, generating the PWM wave by taking the output of the proportional-integral controller as the duty cycle, and controlling the corresponding switching tube of the bidirectional Buck-Boost circuit.

[0043] The specific steps of S4 include:

[0044] S41, subtracting the key load power from the key load power reference value to obtain the error;

[0045] S42, inputting the error into the proportional-integral controller;

[0046] S43, generating the PWM wave by taking the output of the proportional-integral controller as the duty cycle.

[0047] S44, if the error is greater than 0.01 times the critical load power reference value, the generated PWM wave is used as the switching signal of the lower bridge arm switch tube in the bidirectional Buck-Boost circuit, and the upper bridge arm switch tube remains closed, if the error is less than-0.01 times the critical load power reference value, the generated PWM wave is used as the switching signal of the upper bridge arm switch tube in the bidirectional Buck-Boost circuit, and the lower bridge arm switch tube remains closed, if the error is between the two, both switch tubes remain closed.

[0048] The application also provides a direct current power spring control system based on the shoot-through power prediction, which can execute the control method, and comprises:

[0049] A measurement module is configured to measure the critical load voltage and the non-critical load voltage in the system.

[0050] A power calculation module is configured to calculate the critical load power and the non-critical load power under the condition of a pure resistive load according to the measured critical load voltage and non-critical load voltage by using Ohm's law.

[0051] A three-port active bridge control module is configured to calculate the phase shift angle of the current two-port and three-port according to the calculated critical load power and non-critical load power, the phase shift angle of the two-port and three-port in the phase shift control of the three-port active bridge at the previous moment, and the circuit parameters, and apply the phase shift control to the full-bridge converter of the two-port and three-port, so as to realize the control of the three-port active bridge.

[0052] A bidirectional Buck-Boost circuit control module is configured to calculate the error according to the actual power of the critical load and the power reference value, input the error into a proportional-integral controller, take the output of the proportional-integral controller as the duty cycle to generate a PWM wave, and control the upper and lower bridge arm switch tubes of the bidirectional Buck-Boost circuit according to the size relationship between the error and 0.01 times and-0.01 times the critical load power reference value.

[0053] The application will be further described below by means of embodiments and in conjunction with the drawings:

[0054] The system is simulated in MATLAB / Simulink, the DC bus voltage is 20V DC power, the transformer ratio is 1:2:1, the leakage inductance of the three ports of the transformer is 47μH, 330μH and 47μH respectively, the critical load is a pure resistor of 100Ω, the non-critical load is a pure resistor of 25Ω, the voltage stabilizing capacitors of the three ports of the three-port active bridge are 330μF, 470μF and 330μF respectively, the inductance of the bidirectional Buck-Boost circuit is 330μH, the capacitance is 470μF, the voltage of the battery is 12V, and the sampling frequency and the carrier frequency are both 10kHz.

[0055] As shown in Figure 3 the two-port power reference value is 20W, the two-port power reference value is suddenly changed from 20W to 16W at 0.1s, the three-port power reference value is 20W, the three-port power reference value is suddenly changed from 20W to 24W at 0.15s, the control method plays a control effect on the two-port and three-port power, and has no effect on the power size of the other port after stabilization.

[0056] The above examples only illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the present application.

Claims

1. A DC power spring control method based on deadbeat power prediction, used for power control of a DC power spring circuit topology; the DC power spring circuit topology includes a DC bus, a three-port active bridge, a critical load, a non-critical load, a bidirectional Buck-Boost circuit, and a battery; the DC bus is connected to one port of the three-port active bridge, the non-critical load is connected to the second port of the three-port active bridge, the critical load is connected to the third port of the three-port active bridge, the bidirectional Buck-Boost circuit is connected between the critical load and the battery, and each port includes a full-bridge converter; Its features are, The control method is as follows: Measure the voltage of critical and non-critical loads in the circuit topology; Based on the measured critical load and non-critical load voltages, calculate the critical load and non-critical load power under purely resistive load using Ohm's law; Using the calculated critical load and non-critical load power, as well as the critical load and non-critical load power reference values, and the phase shift angles of the two-port and three-port converters at the previous moment, the phase shift angles of the two-port and three-port converters at the current moment are calculated based on the discretized power model prediction equations of the three-port active bridge under phase shift control. The phase shift angles of the two-port and three-port converters are then applied to the full-bridge converters of the two-port and three-port converters through phase shift control to achieve power control. Using the critical load power reference value and the calculated critical load power, the error is calculated, the error is input into the proportional-integral controller, and the output of the proportional-integral controller is used as the duty cycle to generate a PWM wave. Based on the relationship between the error and the critical load power reference value, control the switching transistors of the upper and lower bridge arms of the bidirectional Buck-Boost circuit.

2. The DC power spring control method based on deadbeat power prediction according to claim 1, characterized in that, The discretized power model prediction equations for the three-port active bridge under phase-shift control are as follows: Where P2 and P3 are the non-critical load power and critical load power calculated at the current moment, respectively, P 2ref and P 3ref These are the reference values ​​for non-critical load power and critical load power, respectively. V1 is the rated voltage of port one of the three-port active bridge. V2 and V3 are the rated voltages of ports two and three of the three-port active bridge after being normalized to port one via the transformer, respectively. s To control the frequency, L 12 L 13 and L 23 These are the three leakage inductances under the Δ-type equivalent model of the primary side of a three-port active bridge transformer. and These are the phase shift angles between port 1 and port 2, and between port 1 and port 3, respectively. and These are the correction amounts for the phase shift angle between port 1 and port 2, and the correction amounts for the phase shift angle between port 1 and port 3, respectively.

3. The DC power spring control method based on deadbeat power prediction according to claim 2, characterized in that, The correction amounts for the phase shift angle between port one and port two, and between port one and port three, are as follows:

4. The DC power spring control method based on deadbeat power prediction according to claim 1, characterized in that, The power control steps are as follows: Based on the discretized power model prediction equations of the three-port active bridge under phase-shift control, the corrections for the phase shift angle between port 1 and port 2, and between port 1 and port 3, are calculated. The correction amount of the phase shift angle between port 1 and port 2 is added to the phase shift angle of port 2 at the previous moment to obtain the phase shift angle of port 2 at the current moment; the correction amount of the phase shift angle between port 1 and port 3 is added to the phase shift angle of port 3 at the previous moment to obtain the phase shift angle of port 3 at the current moment. If the phase shift angle of the two-port terminal is less than 0 at the current time, set it to 0; if it is greater than π / 2, set it to π / 2. If the phase shift angle of the three-port terminal is less than 0 at the current time, set it to 0; if it is greater than π / 2, set it to π / 2. The control signals of the four switches of the one-port full-bridge converter are delayed by the phase shift angle of the two ports to obtain the control signals of the four switches of the two-port full-bridge converter; the control signals of the four switches of the one-port full-bridge converter are delayed by the phase shift angle of the three ports to obtain the control signals of the four switches of the three-port full-bridge converter. Among them, the control signals of the four switches of the one-port full-bridge converter are square waves of fixed frequency, and the control signals of the two switches in the same bridge arm are complementary, and the control signals of the two switches connected to the same polarity terminal on the DC side are complementary.

5. The DC power spring control method based on deadbeat power prediction according to claim 1, characterized in that, The steps for controlling the bidirectional Buck-Boost circuit are as follows; The error is obtained by subtracting the calculated critical load power from the critical load power reference value. The error is input to the proportional-integral controller, and the output of the proportional-integral controller is used as the duty cycle to generate a PWM wave. If the error is greater than 0.01 times the critical load power reference value, the generated PWM wave is used as the switching signal for the lower bridge arm switch in the bidirectional Buck-Boost circuit, while the upper bridge arm switch remains off; if the error is less than -0.01 times the critical load power reference value, the generated PWM wave is used as the switching signal for the upper bridge arm switch in the bidirectional Buck-Boost circuit, while the lower bridge arm switch remains off; if the error is between -0.01 times and 0.01 times the critical load power reference value, both the upper and lower bridge arm switches remain off.

6. A DC power spring control system based on deadbeat power prediction, used for power control of a DC power spring circuit topology; the DC power spring circuit topology includes a DC bus, a three-port active bridge, a critical load, a non-critical load, a bidirectional Buck-Boost circuit, and a battery; the DC bus is connected to one port of the three-port active bridge, the non-critical load is connected to the second port of the three-port active bridge, the critical load is connected to the third port of the three-port active bridge, the bidirectional Buck-Boost circuit is connected between the critical load and the battery, and each port includes a full-bridge converter; Its features are, The control system includes: The measurement module is used to measure the voltage of critical and non-critical loads in the circuit topology; The power calculation module is used to calculate the power of critical and non-critical loads under purely resistive loads based on the measured critical and non-critical load voltages and Ohm's law. The three-port active bridge control module is used to calculate the phase shift angles of the two-port and three-port ports at the current moment by using the calculated critical load and non-critical load power, critical load and non-critical load power reference values, and the phase shift angles of the two-port and three-port ports at the previous moment, according to the discretized power model prediction equations of the three-port active bridge under phase shift control. The phase shift angles of the two-port and three-port ports are then applied to the full-bridge converters of the two-port and three-port ports through phase shift control to achieve power control. The bidirectional Buck-Boost circuit control module is used to calculate the error using the critical load power reference value and the calculated critical load power, input the error into the proportional-integral controller, and use the output of the proportional-integral controller as the duty cycle to generate a PWM wave; according to the relationship between the error and the critical load power reference value, it controls the switching transistors of the upper and lower bridge arms of the bidirectional Buck-Boost circuit.

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