Direct-current power spring control method and system based on deadbeat power prediction

Abstract

The invention discloses a direct-current power spring control method and system based on deadbeat power prediction, which are used for performing power control on a direct-current power spring circuit topology. Comprising the following steps: calculating key and non-key load power according to measured key and non-key load voltages; calculating the current phase shift angles of two ports and three ports according to a discretized system power model prediction equation set of the three-port active bridge under phase shift control by using the calculated key and non-key load power and the phase shift angles of the two ports and the three ports in the phase shift control of the three-port active bridge at the previous moment; phase-shift control is applied to a two-port full-bridge converter and a three-port full-bridge converter, so that the control of a three-port active bridge is realized; meanwhile, when the deviation between the actual power value and the reference value of the key load is large, the duty ratio of PWM modulation is obtained according to proportional-integral control, PWM control is applied to the bidirectional Buck-Boost circuit, and control over the bidirectional Buck-Boost circuit is achieved.

Description

Technical Field

[0001] The present invention relates to a control method and system for a direct current (DC) power spring based on deadbeat power prediction, belonging to the technical field of power electronics applications. Background Art

[0002] Driven by global energy tension and energy conservation and emission reduction, distributed generation technology has attracted much attention. However, directly connecting distributed power sources to the grid not only has low economic benefits but may also 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, which will cause resource waste. The application of microgrids can well solve this problem. Compared with AC microgrids, DC microgrids have advantages in household scenarios because they reduce multiple power conversion modules from distributed power sources to loads, which can effectively improve efficiency and economy. In addition, in DC microgrids, usually only active power is concerned, and the relevant voltage can be controlled, so it has attracted much attention from scholars.

[0003] The control of DC microgrids is relatively simple and has been developed relatively maturely. There are already various implementation schemes. The main principle is to control the relevant voltage by enabling the energy storage module to charge and discharge electrical energy to ensure that the microgrid can be stably controlled. However, the frequent electrical energy exchange of the energy storage module will lead to a reduction in its lifespan and efficiency. In addition, the economy of large-capacity energy storage devices and the inconvenience of centralized management also have obvious drawbacks. Therefore, in distributed DC microgrids, making the energy storage module more efficient, more durable, and more cost-effective is a hot topic in the industry. The power spring is one of the solutions, which aims to achieve more stable and efficient operation of the energy storage module and the entire system through reasonable power distribution.

[0004] At present, the control algorithms of DC power springs have been developed to some extent, but there is little research on power control, and there is still no power control strategy based on prediction methods. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a control method and system for a DC power spring based on deadbeat power prediction, which is used for power control of the DC power spring circuit topology.

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

[0007] A control method for a DC power spring based on deadbeat power prediction is used to control the power 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;

[0008] The specific control method is as follows:

[0009] Measure the voltages of the critical load and the non-critical load in the circuit topology;

[0010] According to the measured voltages of the critical load and the non-critical load, use Ohm's law to calculate the powers of the critical load and the non-critical load under pure resistive loads;

[0011] Use the calculated powers of the critical load and the non-critical load, the reference values of the powers of the critical load and the non-critical load, and the phase-shifting angles of the second port and the third port at the previous moment. According to the discrete power model prediction equations of the three-port active bridge under phase-shift control, calculate the phase-shifting angles of the second port and the third port at the current moment, and apply the corresponding phase-shifting angles of the second port and the third port to the full-bridge converters of the second port and the third port through phase-shift control to achieve power control;

[0012] Use the reference value of the critical load power and the calculated critical load power to calculate the error, input the error into a proportional-integral controller, and use the output of the proportional-integral controller as the duty cycle to generate a PWM wave; control the upper and lower bridge arm switching tubes of the bidirectional Buck-Boost circuit according to the magnitude relationship between the error and the reference value of the critical load power.

[0013] A DC power spring control system based on deadbeat power prediction is used to control the power 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;

[0014] The control system includes:

[0015] A measurement module for measuring the voltages of the critical load and the non-critical load in the circuit topology;

[0016] A power calculation module, which is used to calculate the power of the critical load and the non-critical load under the pure resistive load according to the measured critical load and non-critical load voltages by using Ohm's law;

[0017] A three-port active bridge control module, which is used to calculate the phase-shifting angles of the two-port and the three-port at the current moment according to the calculated power of the critical load and the non-critical load, the reference values of the power of the critical load and the non-critical load, and the phase-shifting angles of the two-port and the three-port at the previous moment, based on the discrete power model prediction equations of the three-port active bridge under phase-shift control, and apply the corresponding phase-shifting angles of the two-port and the three-port to the full-bridge converters of the two-port and the three-port through phase-shift control to achieve power control;

[0018] A bidirectional Buck-Boost circuit control module, which is used to calculate the error by using the reference value of the critical load power and the calculated power of the critical load, input the error into a proportional-integral controller, and use the output of the proportional-integral controller as the duty cycle to generate a PWM wave; and control the upper and lower bridge arm switching tubes of the bidirectional Buck-Boost circuit according to the magnitude relationship between the error and the reference value of the critical load power.

[0019] Compared with the prior art, the present invention adopts the above technical solutions and has the following technical effects:

[0020] 1. For the control method proposed by the present invention, by using the discrete power model prediction equations of the three-port active bridge under phase-shift control, the phase-shifting angles of the two-port and the three-port at the next moment are calculated, and the phase-shifting angles are applied to the full-bridge converters of the two-port and the three-port through phase-shift control, so as to achieve the power control effect on the DC power spring system.

[0021] 2. For the control method proposed by the present invention, the core of the control lies in the phase-shifting angle calculation equations of the two-port and the three-port. Only the phase-shifting angles need to be calculated according to the circuit parameters and the measured values and applied to the full-bridge converter. The dynamic response is relatively fast, the structure is simple and easy to implement, and the control of the three-port active bridge part does not require the tuning of the PI controller parameters. Description of the Drawings

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

[0023] Figure 2 is the flowchart of the control method of the present invention;

[0024] Figure 3 are the power waveforms of the two-port and the three-port when the given value of the two-port power is 20 W and becomes 16 W at 0.1 s, and the given value of the three-port power is 20 W and becomes 24 W at 0.15 s. Detailed Embodiments

[0025] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention.

[0026] As Figure 1 shown, a direct current power spring control method based on deadbeat power prediction, and the applied circuit topology includes: a direct current bus, a three-port active bridge, a critical load, a non-critical load, a bidirectional Buck-Boost circuit, and a storage battery; 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, and the bidirectional Buck-Boost circuit is connected to the critical load and the storage battery; according to the system power model prediction equations of the discretized three-port active bridge under phase-shift control, taking the reference values of the critical load and non-critical load powers as the actual system power values predicted at the next moment, calculate the phase-shift angles that should be had by the current second port and third port.

[0027] In Figure 1 , V dc is the direct current bus, C 1 , C 2 and C 3 are the voltage stabilizing capacitors of the first port, second port, and third port respectively, L 1 , L 2 and L 3 are the leakage inductances of the transformers of the first port, second port, and third port respectively, R 2 is the non-critical load, R 3 is the critical load, S 2 and S 1 are the upper and lower bridge arm switching tubes of the bidirectional Buck-Boost circuit respectively, L b is the inductor of the bidirectional Buck-Boost circuit, C b is the capacitor of the bidirectional Buck-Boost circuit, V battery is the storage battery.

[0028] As Figure 2 shown, a direct current power spring control method based on deadbeat power prediction includes the following steps:

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

[0030] S2, according to the measured voltages of the critical load and non-critical load, use Ohm's law to calculate the powers of the critical load and non-critical load under the pure resistive load.

[0031] S3. Using the calculated critical load and non-critical load powers, the reference values of the critical load and non-critical load powers, the two-port and three-port phase-shifting angles at the previous moment, and the circuit parameters, calculate the two-port and three-port phase-shifting angles at the next moment according to the discretized power equation set of the three-port active bridge under phase-shift control, and apply the phase-shifting angles to the full-bridge converters of the two-port and three-port through phase-shift control to achieve power control.

[0032] The specific steps of S3 include:

[0033] S31. Calculate the correction amount of the two-port phase-shifting angle and the correction amount of the three-port phase-shifting angle according to the discretized power model prediction equation set of the three-port active bridge under phase-shift control.

[0034] The discretized power model prediction equation set of the three-port active bridge under phase-shift control is as follows:

[0035]

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

[0037]

[0038] S32. Superimpose the correction amounts of the two-port and three-port phase-shifting angles on the two-port and three-port phase-shifting angles of the previous control respectively to obtain the new two-port and three-port phase-shifting angles.

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

[0040] S34. Delay the control signals of the four switching tubes of the one-port full-bridge converter by the two-port phase-shifting angle and the three-port phase-shifting angle respectively to obtain the control signals of the four switching tubes of the two-port and three-port full-bridge converters, where the control signals of the four switching tubes of the one-port full-bridge converter are square waves with a fixed frequency, and the control signals of the two switching tubes in 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. Calculate the error using the actual power and power reference value of the critical load, input the error into the proportional-integral controller, use the output of the proportional-integral controller as the duty cycle to generate a PWM wave, and control the upper and lower bridge arm switching tubes of the bidirectional Buck-Boost circuit according to the magnitude relationship between the error and 0.01 times and -0.01 times the critical load power reference value.

[0042] Whether it exceeds the limit. If it exceeds the limit, input the error into the proportional-integral controller, use the output of the proportional-integral controller as the duty cycle to generate a PWM wave, and control the corresponding switching tubes of the bidirectional Buck-Boost circuit.

[0043] The specific steps of S4 include:

[0044] S41. Subtract the critical load power from the critical load power reference value to obtain an error;

[0045] S42. Input the error into a proportional-integral controller;

[0046] S43. Use the output of the proportional-integral controller as the duty cycle to generate a PWM wave;

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

[0048] The present invention also proposes a DC power spring control system based on deadbeat power prediction, which can execute the above control method, including:

[0049] Measurement module: Measure the voltages of the critical load and non-critical load in the system;

[0050] Power calculation module: According to the measured voltages of the critical load and non-critical load, use Ohm's law to calculate the critical load and non-critical load powers in the case of a pure resistive load;

[0051] Three-port active bridge control module: Use the calculated critical load and non-critical load powers, the phase-shift angles of the second port and the third port in the three-port active bridge phase-shift control at the previous moment, and the circuit parameters to calculate the current phase-shift angles that the second port and the third port should have, and apply phase-shift control to the full-bridge converters of the second port and the third port to achieve the control of the three-port active bridge.

[0052] And, bidirectional Buck-Boost circuit control module: Use the actual power and power reference value of the critical load to calculate an error, input the error into a proportional-integral controller, use the output of the proportional-integral controller as the duty cycle to generate a PWM wave, and control the upper and lower arm switch tubes of the bidirectional Buck-Boost circuit according to the magnitude relationship between the error and 0.01 times and -0.01 times the critical load power reference value.

[0053] The following further illustrates the present invention through embodiments in conjunction with the accompanying drawings:

[0054] The system is simulated in MATLAB / Simulink. During the simulation, the DC bus voltage is 20V DC, the transformer turns ratio is 1:2:1, the leakage inductances of the three ports of the transformer are 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 inductor of the bidirectional Buck-Boost circuit is 330μH, the capacitor is 470μF, the voltage of the battery is 12V, and the sampling frequency and the carrier frequency are both 10kHz.

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

[0056] The above embodiments are only used to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the present invention.

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; It is characterized in that The control method is specifically as follows: Measure critical load and non-critical load voltages in circuit topologies; According to the measured critical load and non-critical load voltages, the critical load and non-critical load powers under pure resistive load are calculated using Ohm's law; Using the calculated critical load and non-critical load power and critical load and non-critical load power reference values, the phase shift angles of the two-port and three-port at the previous moment, and according to the discretized power model prediction equation group of the three-port active bridge under phase shift control, the phase shift angles of the two-port and three-port at the current moment are calculated, and the two-port and three-port phase shift angles are correspondingly applied to the two-port and three-port full-bridge converters through phase shift control to realize power control; Using the key load power reference value and the calculated key load power, an error is calculated, 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 relationship between the error and the key load power reference value, the upper and lower bridge arm switches of the bidirectional Buck-Boost circuit are controlled.

2. The DC power spring control method based on deadbeat power prediction according to claim 1, characterized in that: The discretized power model prediction equation group of the three-port active bridge under the phase shift control is as follows: Among them, P2 and P3 are the non-critical load power and critical load power calculated at the current moment, respectively. 2ref and P 3ref are the non-critical load power reference value and the critical load power reference value, respectively. V1 is the rated voltage of the first port of the three-port active bridge. V2 and V3 are the rated voltages of the second and third ports of the three-port active bridge after being converted to the first port through the transformer. f s To control the frequency, L 12 , L 13 and L 23 They are the three leakage inductances under the Δ-type equivalent model of the primary side of the three-port active bridge transformer, and are the phase shift angles between port 1 and port 2, and between port 1 and port 3, respectively. and They are respectively the correction amount of the phase shift angle between port 1 and port 2, and the correction amount of the phase shift angle between port 1 and port 3.

3. The DC power spring control method based on deadbeat power prediction according to claim 2, characterized in that: The correction amount of the phase shift angle between the first port and the second port, and the correction amount of the phase shift angle between the first port and the third port are specifically as follows:

4. The DC power spring control method based on deadbeat power prediction according to claim 1, characterized in that: The steps of power control are as follows: According to the discretized power model prediction equation group of the three-port active bridge under phase shift control, the correction amount of the phase shift angle between the first port and the second port and the correction amount of the phase shift angle between the first port and the third port are calculated; The correction amount of the phase shift angle between the first port and the second port is superimposed on the phase shift angle of the second port at the previous moment to obtain the phase shift angle of the second port at the current moment; the correction amount of the phase shift angle between the first port and the third port is superimposed on the phase shift angle of the third port at the previous moment to obtain the phase shift angle of the third port at the current moment; If the phase shift angle of the two-port at the current moment is less than 0, set it equal to 0; if it is greater than π / 2, set it equal to π / 2; if the phase shift angle of the three-port at the current moment is less than 0, set it equal to 0; if it is greater than π / 2, set it equal to π / 2; The control signals of the four switch tubes of the one-port full-bridge converter are lagged by two-port phase shift angles to obtain the control signals of the four switch tubes of the two-port full-bridge converter; the control signals of the four switch tubes of the one-port full-bridge converter are lagged by three-port phase shift angles to obtain the control signals of the four switch tubes of the three-port full-bridge converter; wherein, the control signals of the four switch tubes of the one-port full-bridge converter are square waves of fixed frequency, and the control signals of the two switch tubes in the same bridge arm are complementary, and the control signals of the two switch tubes connected to the same polarity end of 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 of bidirectional Buck-Boost circuit control are as follows: The error is obtained by subtracting the calculated key load power from the key load power reference value; 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; 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 arm switch tube in the bidirectional Buck-Boost circuit, and the upper arm switch tube remains turned 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 of the upper arm switch tube in the bidirectional Buck-Boost circuit, and the lower arm switch tube remains turned off; if the error is between -0.01 times and 0.01 times the critical load power reference value, both the upper and lower arm switch tubes remain turned 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; It is characterized in that The control system comprises: A measurement module for measuring the voltage of critical loads and non-critical loads in the circuit topology; A power calculation module, used for calculating the critical load and non-critical load power under a pure resistive load by using Ohm's law according to the measured critical load and non-critical load voltages; The three-port active bridge control module is used to use the calculated critical load and non-critical load power and the critical load and non-critical load power reference values, the phase shift angles of the two-port and the three-port at the previous moment, and the discretized power model prediction equation group of the three-port active bridge under phase shift control to calculate the phase shift angles of the two-port and the three-port at the current moment, and apply the two-port and three-port phase shift angles to the two-port and three-port full-bridge converters through phase shift control to achieve power control; The bidirectional Buck-Boost circuit control module is used to calculate the error using the key load power reference value and the calculated key 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 key load power reference value, the upper and lower bridge arm switches of the bidirectional Buck-Boost circuit are controlled.

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