Unidirectional energy storage DC-DC converter control system and method for wave power generation

Abstract

The invention discloses a unidirectional energy storage DC-DC converter control system and method for wave power generation. The unidirectional energy storage DC-DC converter control system comprises a bridge rectifier unit, a hybrid full-half bridge DC-AC unit, a double-transformer unit, a resonance unit, a high-frequency AC-DC full-bridge unit and a DC bus, in the system, a bridge rectifier unit, a hybrid full-half-bridge DC-AC unit, a double-transformer unit, a resonance unit, a high-frequency AC-DC full-bridge unit and a direct-current bus are connected in sequence, and stable direct-current voltage is provided for the direct-current bus. Due to the fact that the wave power generation system has the problems that active devices are damaged due to large voltage fluctuation in the electric energy conversion process and conversion efficiency is reduced due to high backflow power, the double-loop topological structure and the minimum power loss control method are adopted, and the method can be suitable for the electric energy conversion system in wave power generation. According to the system, zero backflow power can be realized, conduction loss is reduced, and the electric energy conversion efficiency of the system and the quality of output electric energy are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of DC-DC converter control, and in particular to a unidirectional energy storage DC-DC converter control system and method for wave power generation. Background Art

[0002] The wave power generation power conversion system converts wave energy into mechanical energy, and then into electrical energy to provide voltage for the DC bus. Due to the large volatility of waves, calm or large waves will affect its output voltage. The use of ordinary uncontrolled rectification makes the circuit difficult to control due to the large changes in the DC side voltage. In addition, due to the immature technology, these devices will generate a large output power, resulting in large losses and low efficiency during the transmission process. Summary of the invention

[0003] The purpose of the present invention is to provide a unidirectional energy storage DC-DC converter control system and method for wave power generation, which eliminates output power, realizes soft switching, reduces conduction loss, and greatly improves the power transmission efficiency of the system.

[0004] The technical solution to achieve the purpose of the present invention is: A unidirectional energy storage DC-DC converter control system for wave power generation, comprising a wave power generation device and a bridge rectifier unit connected to the wave power generation device, wherein the bridge rectifier unit is connected to a hybrid full-half bridge DC-AC unit, the output end of the hybrid full-half bridge DC-AC unit is connected to a primary side of a dual transformer unit, and a dual-loop topology structure is formed by a full-bridge and half-bridge connection mode; the secondary side of the dual transformer unit is connected to an input end of a high-frequency AC-DC full-bridge unit through a resonance unit, and the output end of the high-frequency AC-DC full-bridge unit is connected to a DC bus, providing a stable DC voltage for the DC bus; The resonant current phase adjustment module is also included to adjust the resonant current Zero adjustment at γ Therefore, the resonant current and the voltage waveform are in phase, eliminating the reactive power of the high-frequency rectifier bridge.

[0005] In the preferred technical solution, the hybrid full half-bridge DC-AC unit includes a voltage-sharing capacitor C 1 , C 2 , and switch tube S 1 ~ S 4 The high frequency AC-DC full bridge unit includes a switch tube Q 1 , Q 2 and diode D1 , D 2 The dual transformer device is composed of two transformers, including a full-bridge transformer and a half-bridge transformer. The primary side of the full-bridge transformer is connected S 1 , S 2 Bridge arm midpoint and connection S 3 , S 4 The full-bridge transformer at the midpoint of the bridge arm, the primary side of the half-bridge transformer is connected S 1 , S 2 The midpoint of the bridge arm and C 1 , C 2 A half-bridge transformer at the midpoint of the voltage-equalizing capacitor forms a dual-loop topology of a full-bridge and a half-bridge on the primary side, wherein the secondary side of the full-bridge transformer is connected to one end of the secondary side of the half-bridge transformer; the other end of the secondary side of the full-bridge transformer is connected to a diode through a resonant unit. D 1 , D 2 The other end of the secondary side of the half-bridge transformer is connected to the switch tube Q 1 , Q 2 The midpoint of the bridge arm.

[0006] The preferred technical solution also includes controlling the switch tube S 1 The pulse width is 0, the switch tube S 2 The pulse width is π , switch tube S 3 The pulse width is α arrive π + α , switch tube S 4 The pulse width is π + α arrive 2π + α ; and the switch tube S 3 Hysteresis switch S 1 Angle α ; This generates an AC voltage , for S 1 , S 2The midpoint of the bridge arm and S 3 , S 4 The voltage between the midpoints of the bridge arms, contain +V 1 , -V 1 , 0 three voltage levels; generate AC voltage , for S 1 , S 2 The midpoint of the bridge arm and C 1 , C 2 The voltage between the points in the grading capacitor is contain +1 / 2V 1 , -1 / 2V 1 Two voltage levels, V 1 is the input voltage.

[0007] The preferred technical solution also includes controlling the switch tube Q 1 The pulse width is β arrive π + β , switch tube Q 2 The pulse width is π + β arrive 2π + β , which generates an AC voltage , is the voltage between the midpoint of diodes D1 and D2 and the midpoint of the bridge arms of switches Q1 and Q2. contain +V 2 , -V 2 , 0 three voltage levels, V 2 is the output voltage.

[0008] The preferred technical solution also includes using the fundamental wave approximation analysis method to perform steady-state analysis to obtain , and The fundamental phasors of the three voltages are expressed as right , and After normalization, the normalized phasor expression is as follows: ;

[0009] ;

[0010] ;

[0011] In the formula, yes The normalized vector of ; yes The normalized vector of ; yes The normalized vector of ; is the basic value; is the voltage gain; The preferred technical solution also includes: and Merge into , simplify the circuit and get the equivalent circuit diagram : .

[0012] According to the normalized switching frequency , quality factor , we get the normalized impedance of the capacitor: ; in, is the switching angular frequency, is the normalized resonant angular frequency, is the resonant capacitor, is the resonant inductor; in, is the normalized impedance, is the load resistance and n is the transformer ratio coefficient.

[0013] According to the equivalent circuit diagram, the normalized resonant current expression is: .

[0014] in, ; in, .

[0015] The preferred technical solution also includes, according to the formula Calculate normalized power : .

[0016] The resonant current is obtained according to the minimum power loss control method Effective value : .

[0017] The preferred technical solution also includes establishing a steady-state model of the resonant current and the output power according to the obtained steady-state model of the resonant current and the output power. The Lagrange equation is: .

[0018] in, is the Lagrangian optimization function; is a scalar value; C is a constraint condition; Will right Taking partial derivatives we get: ;

[0019] in, .

[0020] Will right Taking partial derivatives we get: ;

[0021] Will right Taking partial derivatives we get: ;

[0022] Simplifying the above three equations, we can get the zero reflux control method relationship: .

[0023] Substitute the minimum power loss control method relationship into Simplified to get the minimum power loss : .

[0024] control of Pulse Width right to control the size.

[0025] A control method for a unidirectional energy storage DC-DC converter for wave power generation is applied to the above-mentioned unidirectional energy storage DC-DC converter control system for wave power generation. The control method comprises the following steps: S01: Control switch tube S 1 The pulse width is 0, the switch tube S 2 The pulse width is π , switch tube S 3 The pulse width is α arrive π +α , switch tube S 4 The pulse width is π + α arrive 2π + α ; and the switch tube S 3 Hysteresis switch S 1 Angle α ; This generates an AC voltage , for S 1 , S 2 The midpoint of the bridge arm and S 3 , S 4 The voltage between the midpoints of the bridge arms; generating an AC voltage , for S 1 , S 2 The midpoint of the bridge arm and C 1 , C 2 The voltage between the points in the grading capacitor; S02: Control switch tube Q 1 The pulse width is β arrive π + β , switch tube Q 2 The pulse width is π + β arrive 2π + β , which generates an AC voltage , It is the voltage between the midpoint of diodes D1 and D2 and the midpoint of the bridge arms of switches Q1 and Q2; S03: Resonant current Adjust the phase of the resonant current: Zero adjustment at γ Therefore, the resonant current and the voltage waveform are in phase, eliminating the reactive power of the high-frequency rectifier bridge.

[0026] The present invention further discloses a computer storage medium on which a computer program is stored. When the computer program is executed, the control method of the control system of the unidirectional energy storage DC-DC converter for wave power generation is realized.

[0027] Compared with the prior art, the present invention has the following significant advantages: (1) The present invention proposes an electric energy conversion system suitable for wave energy generation. Its topology adopts two diodes on the secondary side to replace the traditional MOS switch tube, reducing the switch tube loss and the cost of converter manufacturing. The primary side adopts full-bridge and half-bridge connection modes to form a dual-loop topology structure, realizing four voltage levels. The high-frequency AC voltage level can reach up to 1.5 times the input voltage, further reducing the current stress and extending the service life of active devices and high-frequency transformers.

[0028] (2) The present invention utilizes a minimum power loss control method to optimize the problem of excessive reflux power on the output side and low converter operating efficiency, thereby achieving minimum conduction power loss and improving system efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the control system schematic diagram of a unidirectional energy storage DC-DC converter for wave power generation; Figure 2 By controlling the switch S 1 ~ S 4 And switch tube Q 1 , Q 2 The generated AC voltage waveform and resonant current waveform diagram; Figure 3 It is the equivalent circuit diagram in the phasor domain of the unidirectional energy storage DC-DC converter control system for wave power generation established using FHA; Figure 4 When M =0.5, k=1, V 1 =150V, V 2 =75V, P =400W, v ab , v ac 、v mn , i L And the current waveform of each switch tube.

[0030] Figure 5 When M =0.5, k=1, V 1 =150V, V 2 =75V, P =200W, v ab ,v ac 、v mn , i L And the current waveform of each switch tube. DETAILED DESCRIPTION

[0031] The principle of the present invention is: since the wave energy power generation system has large voltage fluctuations during the power conversion process, which leads to damage to active devices and high reflux power, which leads to reduced conversion efficiency, the present invention adopts a dual-loop topology structure and a minimum power loss control method to design an energy conversion system that can be used in wave energy power generation. The system can achieve zero reflux power, reduce conduction loss, and greatly improve the system's power conversion efficiency and output power quality.

[0032] Embodiment 1:

[0033] like Figure 1 As shown, the electric energy conversion system suitable for wave energy generation proposed in this case includes a bridge rectifier unit, a hybrid full-half bridge DC-AC unit, a dual transformer unit, a resonance unit, a high-frequency AC-DC full-bridge unit and a DC bus. The wave power generation device is connected to the bridge rectifier unit, the bridge rectifier unit is connected to the hybrid full-half bridge DC-AC unit, the output end of the hybrid full-half bridge DC-AC unit is connected to the primary side of the dual transformer unit, and a full-bridge and half-bridge connection method is used to form a dual-loop topology structure; the secondary side of the dual transformer unit is connected to the input end of the high-frequency AC-DC full-bridge unit through the resonance unit, and the output end of the high-frequency AC-DC full-bridge unit is connected to the DC bus to provide a stable DC voltage for the DC bus.

[0034] In one embodiment, the hybrid full half-bridge DC-AC unit includes a voltage balancing capacitor C 1 , C 2 , and switch tube S 1 ~ S 4 , the high frequency AC-DC full bridge unit includes the switch tube Q 1 , Q 2 and diode D 1 , D 2 The dual transformer device consists of two transformers, including a full-bridge transformer and a half-bridge transformer. The primary side of the full-bridge transformer is connected S 1 , S 2 Bridge arm midpoint and connection S 3, S 4 Full-bridge transformer at the midpoint of the bridge arm, primary connection of half-bridge transformer S 1 , S 2 The midpoint of the bridge arm and C 1 , C 2 The half-bridge transformer at the midpoint of the voltage-equalizing capacitor forms a dual-circuit topology of full-bridge and half-bridge on the primary side. The secondary side of the full-bridge transformer is connected to one end of the secondary side of the half-bridge transformer; the other end of the secondary side of the full-bridge transformer is connected to a diode through a resonant unit. D 1 , D 2 The other end of the secondary side of the half-bridge transformer is connected to the switch tube Q 1 , Q 2 The midpoint of the bridge arm.

[0035] The turns ratio of the full-bridge transformer is n1:1, and the turns ratio of the half-bridge transformer is n2:1. n 2 : n 1 Defined as k.

[0036] Preferably, for better performance, set n 1 = n 2 =n ,Right now k= 1.

[0037] Specifically, the switch S 1 ~S 4 Including body diode d S1 ~ d S4 And parasitic capacitance C S1 ~ C S4 .

[0038] The high-frequency AC-DC full-bridge unit consists of a switch tube Q 1 , Q 2 , Body diode d Q1 , d Q2 , parasitic capacitance CQ1 , C Q2 ,diode D 1 , D 2 、Filter capacitor C 0 And the output voltage V 2 composition.

[0039] The resonant unit consists of a resonant capacitor C s , resonant inductor L s Connect in sequence.

[0040] like Figure 2 As shown, the switch tube in the hybrid full half-bridge DC-AC unit S 1 The pulse width is from 0 to π , switch tube S 2 The pulse width is π arrive 2π , switch tube S 3 The pulse width is α arrive π + α , switch tube S 4 The pulse width is π + α arrive 2π + α ; This generates an AC voltage contain +V 1 , -V 1 , 0 three voltage levels, generating AC voltage contain +1 / 2V 1 , -1 / 2V 1 Two voltage levels, for and The superposition contains +1.5V 1 , -1.5V 1 , +1 / 2V 1 , -1 / 2V 1 Four voltage levels.

[0041] Specifically, the switch tube in the high-frequency AC-DC full-bridge unit Q 1 The pulse width isβ arrive π + β , switch tube Q 2 The pulse width is π + β arrive 2π + β ; This generates an AC voltage contain +V 2 , -V 2 , 0 three voltage levels.

[0042] Specifically, the resonant current Zero adjustment at γ Therefore, the resonant current and the voltage waveform are in phase, the reactive power of the high-frequency rectifier bridge is eliminated, and zero reflux power is achieved.

[0043] In another embodiment, a control method of a unidirectional energy storage DC-DC converter for wave power generation is applied to the above-mentioned unidirectional energy storage DC-DC converter control system for wave power generation, and the control method comprises the following steps: S01: Control switch tube S 1 The pulse width is 0, the switch tube S 2 The pulse width is π , switch tube S 3 The pulse width is α arrive π + α , switch tube S 4 The pulse width is π + α arrive 2π + α ; and the switch tube S 3 Hysteresis switch S 1 Angle α ; This generates an AC voltage , for S 1 , S 2 The midpoint of the bridge arm and S 3 , S 4 The voltage between the midpoints of the bridge arms; generating an AC voltage , for S 1 ,S 2 The midpoint of the bridge arm and C 1 , C 2 The voltage between the points in the grading capacitor; S02: Control switch tube Q 1 The pulse width is β arrive π + β , switch tube Q 2 The pulse width is π + β arrive 2π + β , which generates an AC voltage , It is the voltage between the midpoint of diodes D1 and D2 and the midpoint of the bridge arms of switches Q1 and Q2; S03: Resonant current Adjust the phase of the resonant current: Zero adjustment at γ Therefore, the resonant current and the voltage waveform are in phase, eliminating the reactive power of the high-frequency rectifier bridge.

[0044] Specifically, using the Fundamental Harmonic Approximation (FHA) analysis method for steady-state analysis, we can get , and The fundamental phasors of the three voltages are expressed as right , and After normalization, the normalized phasor expression is as follows: ;

[0045] ;

[0046] ;

[0047] In the formula yes The normalized vector of ; yes The normalized vector of ; yes The normalized vector of ; is the basic value, defined as ; is the voltage gain, defined as .

[0048] Will and The two are combined into , simplify the circuit, such as Figure 3 shown.

[0049] ;

[0050] According to the normalized switching frequency , quality factor The normalized impedance of the capacitor can be obtained: .

[0051] in, is the switching angular frequency, is the normalized resonant angular frequency, is the resonant capacitor, is the resonant inductor.

[0052] in, is the normalized impedance, is the load resistance.

[0053] According to the equivalent circuit diagram, the normalized resonant current expression is: .

[0054] in, .

[0055] in, .

[0056] According to the formula The normalized power can be calculated : .

[0057] Specifically, the minimum power loss control method includes the following processes: .

[0058] According to the obtained steady-state model of resonant current and output power, a The Lagrange equation is: ;

[0059] in, is the Lagrangian optimization function; is a scalar value that measures the impact of the constraint on the function; C is a quantitative constraint.

[0060] Will right Taking partial derivatives we get: .

[0061] in, .

[0062] Will right Taking partial derivatives we get: ;

[0063] Will right Taking partial derivatives we get: ;

[0064] Simplifying the above three equations, we can get the minimum power loss control method relationship: .

[0065] Substitute the minimum power loss control method relationship into Simplification can get the minimum power loss : .

[0066] By formula It can be seen that only control of Pulse Width You can to control the size.

[0067] Another embodiment is a computer storage medium having a computer program stored thereon, wherein the computer program, when executed, implements the control method of the unidirectional energy storage DC-DC converter control system for wave power generation.

[0068] The specific implementation method can adopt the above method, which will not be repeated here.

[0069] In order for the converter to operate efficiently, appropriate parameter design is required: choose Q =1, F =1.4, ω S =200πkHz, L r =31.34μH, C r =158.56nF.

[0070] Design input voltage V 1 The output voltage is 150V V 2 It is 75V and the rated power is 400W.

[0071] By simulating according to the designed input, output voltage and power, all switches can achieve soft switching.

[0072] To verify the correctness of the theory, simulation tests were carried out in PSIM.

[0073] when M =0.5, k=1, V 1 =150V, V 2 =75V, P =400W, v ab , v ac 、v mn , i L And the current waveforms of each switch tube are as follows Figure 4 shown.

[0074] when M =0.5, k=1, V 1 =150V, V 2 =75V, P =200W, v ab , v ac 、v mn , i L And the current waveforms of each switch tube are as follows Figure 5 shown.

[0075] After verification combined with simulation waveforms, it was found that the theory was consistent with practice, proving that the present invention is feasible.

[0076] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement modes and shall be included in the protection scope of the present invention.

Claims

1. A unidirectional energy storage DC-DC converter control system for wave power generation, comprising a wave power generation device and a bridge rectifier unit connected to the wave power generation device, characterized in that: The bridge rectifier unit is connected to the hybrid full-half bridge DC-AC unit, the output end of the hybrid full-half bridge DC-AC unit is connected to the primary side of the dual transformer unit, and a dual-loop topology structure is formed by a full-bridge and half-bridge connection mode; the secondary side of the dual transformer unit is connected to the input end of the high-frequency AC-DC full-bridge unit through a resonance unit, and the output end of the high-frequency AC-DC full-bridge unit is connected to the DC bus, providing a stable DC voltage for the DC bus; The resonant current phase adjustment module is also included to adjust the resonant current Zero adjustment at γ Therefore, the resonant current and the voltage waveform are in phase, eliminating the reactive power of the high-frequency rectifier bridge.

2. The unidirectional energy storage DC-DC converter control system for wave power generation according to claim 1 is characterized in that: The hybrid full half-bridge DC-AC unit includes a voltage grading capacitor C 1 , C 2 , and switch tube S 1 ~ S 4 The high frequency AC-DC full bridge unit includes a switch tube Q 1 , Q 2 and diode D 1 , D 2 The dual transformer is composed of two transformers, including a full-bridge transformer and a half-bridge transformer. The primary side of the full-bridge transformer is connected S 1 , S 2 Bridge arm midpoint and connection S 3 , S 4 The full-bridge transformer at the midpoint of the bridge arm, the primary side of the half-bridge transformer is connected S 1 , S 2 The midpoint of the bridge arm and C 1 , C 2 A half-bridge transformer at the midpoint of the voltage-equalizing capacitor forms a dual-loop topology of a full-bridge and a half-bridge on the primary side, wherein the secondary side of the full-bridge transformer is connected to one end of the secondary side of the half-bridge transformer; the other end of the secondary side of the full-bridge transformer is connected to a diode through a resonant unit. D 1 , D 2 The other end of the secondary side of the half-bridge transformer is connected to the switch tube Q 1 , Q 2 The midpoint of the bridge arm.

3. The unidirectional energy storage DC-DC converter control system for wave power generation according to claim 2 is characterized in that: Also includes, control switch tube S 1 The pulse width is 0, the switch tube S 2 The pulse width is π , switch tube S 3 The pulse width is α arrive π + α , switch tube S 4 The pulse width is π + α arrive 2π + α ; and the switch tube S 3 Hysteresis switch S 1 Angle α ; This generates an AC voltage , for S 1 , S 2 The midpoint of the bridge arm and S 3 , S 4 The voltage between the midpoints of the bridge arms, contain +V 1 , -V 1 , 0 three voltage levels; generate AC voltage , for S 1 , S 2 The midpoint of the bridge arm and C 1 , C 2 The voltage between the points in the grading capacitor is contain +1 / 2V 1 , -1 / 2V 1 Two voltage levels, V 1 is the input voltage.

4. The unidirectional energy storage DC-DC converter control system for wave power generation according to claim 3 is characterized in that: Also includes, control switch tube Q 1 The pulse width is β arrive π + β , switch tube Q 2 The pulse width is π + β arrive 2π + β , which generates an AC voltage, which is the voltage between the midpoint of diodes D1 and D2 and the midpoint of the bridge arms of switches Q1 and Q2, containing +V 2 , -V 2 , 0 three voltage levels, V 2 is the output voltage.

5. The unidirectional energy storage DC-DC converter control system for wave power generation according to claim 4 is characterized in that: It also includes the use of fundamental wave approximation analysis method to perform steady-state analysis and obtain , and The fundamental phasors of the three voltages are expressed as right , and After normalization, the normalized phasor expression is as follows: ， ， ， In the formula, yes The normalized vector of ; yes The normalized vector of ; yes The normalized vector of ; is the basic value; is the voltage gain.

6. The unidirectional energy storage DC-DC converter control system for wave power generation according to claim 5, characterized in that: Also includes, and Merge into , simplify the circuit and get the equivalent circuit diagram : ， According to the normalized switching frequency , quality factor , we get the normalized impedance of the capacitor: ; in, is the switching angular frequency, is the normalized resonant angular frequency, is the resonant capacitor, is the resonant inductor; in, is the normalized impedance; According to the equivalent circuit diagram, the normalized resonant current expression is: ， in, , in, .

7. The unidirectional energy storage DC-DC converter control system for wave power generation according to claim 6, characterized in that: Also included, according to the formula Calculate normalized power : ， The resonant current is obtained according to the minimum power loss control method Effective value : 。 8. The unidirectional energy storage DC-DC converter control system for wave power generation according to claim 7, characterized in that: It also includes establishing a steady-state model of the resonant current and output power according to the obtained The Lagrange equation is: ， in, is the Lagrangian optimization function; is a scalar value, C is a constraint; Will right Taking partial derivatives we get: ， in, , Will right Taking partial derivatives we get: ， Will right Taking partial derivatives we get: ， Simplified zero reflux control method relationship: ， Substitute the minimum power loss control method relationship into Simplified to get the minimum power loss : ， control of Pulse Width right to control the size.

9. A control method for a unidirectional energy storage DC-DC converter for wave power generation, characterized in that: The control method of the unidirectional energy storage DC-DC converter control system for wave power generation according to claim 2 comprises the following steps: S01: Control switch tube S 1 The pulse width is 0, the switch tube S 2 The pulse width is π , switch tube S 3 The pulse width is α arrive π + α , switch tube S 4 The pulse width is π + α arrive 2π + α ; and the switch tube S 3 Hysteresis switch S 1 Angle α ; This generates an AC voltage , for S 1 , S 2 The midpoint of the bridge arm and S 3 , S 4 The voltage between the midpoints of the bridge arms; generating an AC voltage , for S 1 , S 2 The midpoint of the bridge arm and C 1 , C 2 The voltage between the points in the grading capacitor; S02: Control switch tube Q 1 The pulse width is β arrive π + β , switch tube Q 2 The pulse width is π + β arrive 2π + β , which generates an AC voltage , It is the voltage between the midpoint of diodes D1 and D2 and the midpoint of the bridge arms of switches Q1 and Q2; S03: Resonant current Adjust the phase of the resonant current: Zero adjustment at γ Therefore, the resonant current and the voltage waveform are in phase, eliminating the reactive power of the high-frequency rectifier bridge.

10. A computer storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the control method of the unidirectional energy storage DC-DC converter for wave power generation described in claim 9 is implemented.

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