Triple phase-shifting optimization control method for direct-current electric energy converter oriented to integration of source, network and load storage
By introducing triple phase shift optimization control method and fine loss model in DC energy converter, combined with Gurobi solver, the optimal control strategy is calculated, and the problem of loss neglect in traditional control strategies is solved, and efficient power transmission and system performance improvement is achieved .
Patent Information
- Application Number
- CN202411058107.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-02
- Publication Date
- 2024-12-13
AI Technical Summary
The traditional DC energy converter control strategy ignores the loss in the system, resulting in low efficiency, high switching losses, poor dynamic response, difficult to cope with wide range of load changes, and fail to fully consider excitation waveform, current harmonics and frequency conversion effects of conductor regions. Effect on loss.
The triple phase shift optimization control method for source grid-to-load and storage is adopted to optimize the three independent phase differences between the full-bridge circuits on the primary and secondary sides by introducing fine models of conduction loss, switching loss and magnetic component loss. , in combination with Python 3.8, calls the Gurobi solver to calculate the optimal control strategy to reduce losses and improve system performance.
Effectively reduce losses, improve dynamic response, improve overall performance and stability of DC power converters, and significantly improve the reliability and efficiency of the system.
Smart Images
Figure CN119134917A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of optimization design of DC converters, and in particular relates to a triple phase-shift optimization control method for a DC power converter integrated with a source, a grid, a load and a storage. Background Art
[0002] "Source-grid-load-storage integration" is an operation mode and technology that can maximize the utilization of energy resources. Through various forms of interaction such as source-source complementarity, source-grid coordination, grid-load interaction, grid-storage interaction, and source-load interaction, it can improve the power dynamic balance capability of the power system in a more economical, efficient, and safe manner. It is an important development path for building a new power system. The DC power converter is the core equipment for realizing AC / DC power conversion and control in the "source-grid-load-storage integration" system.
[0003] DC power converters are also widely used in many fields such as electric vehicles, renewable energy systems and grid energy storage due to their high efficiency, bidirectional energy transmission capability and flexible power control characteristics. However, the traditional DC power converter control strategy usually assumes that the system is ideal during the design process and ignores the losses in actual applications, which greatly limits the performance of the system and the improvement of efficiency. With the increase in application requirements and the development of technology, further improving the efficiency of DC power converters has become a research hotspot, so the research on optimizing control strategies is particularly important.
[0004] The traditional control strategy of DC power converter mainly adopts single phase shift control method, which controls the power flow by adjusting the phase difference between the full bridge arms on the primary side and the secondary side of the transformer. However, the single phase shift control method has the disadvantages of low efficiency, high switching loss, poor dynamic response, insufficient control flexibility, and difficulty in coping with wide range of load changes. In response to this problem, a variety of improvement methods have been proposed in recent years, such as extended phase shift optimization control strategy, dual phase shift optimization control strategy and triple phase shift optimization control strategy. Among them, the optimization strategy based on triple phase shift control method has attracted much attention due to its superior regulation ability, which can achieve more precise power control under different working conditions, thereby reducing losses and improving efficiency.
[0005] In order to optimize the performance of DC power converters, various losses in the system must be fully considered, including conduction loss, switching loss, and magnetic component loss. In the current optimization control strategy, the optimization objectives are mainly concentrated on current stress, return power, zero voltage soft switching, and transmission power. These objectives are selected to improve the efficiency and stability of DC power converters. Reducing current stress can extend the life of switching devices, reducing return power can reduce unnecessary energy loss, achieving zero voltage soft switching can reduce switching losses, and optimizing transmission power can help improve the power density and overall efficiency of the system. However, although these optimization objectives can theoretically improve the performance of DC power converters, in practical applications, many strategies fail to fully consider the losses in the system. For example, the effects of excitation waveforms, current harmonics, and frequency-varying effects of conductor regions on losses are simplified or ignored in many models. Current harmonics and frequency-varying effects of conductor regions significantly increase the copper loss of magnetic components, while there is a complex nonlinear relationship between the iron loss of magnetic components and the excitation waveform. These factors are particularly important in high-frequency and high-power applications, but they are not fully considered in many optimization strategies, thus limiting the improvement of system performance. Summary of the invention
[0006] The present invention provides a triple phase shift optimization control method for a DC power converter with integrated source, grid, load and storage. The method introduces a fine model of conduction loss, switching loss and magnetic component loss to comprehensively analyze the impact of these losses on system performance. At the same time, combined with the triple phase shift control method, the three independent phase differences between the primary and secondary full-bridge circuits are optimized to achieve efficient power transmission under different load conditions. The method can effectively reduce losses, improve dynamic response, and enhance the performance and stability of the overall system in high-frequency and high-power application scenarios.
[0007] The technical solution adopted by the present invention is:
[0008] A triple phase shift optimization control method for a DC power converter with integrated source, grid, load and storage comprises the following steps:
[0009] Step 1: Analyze the working waveform characteristics of the DC power converter under the triple phase shift control mode, and derive the simplified circuit model and the inductor current and transmission power function expressions;
[0010] Step 2: In the DC power converter structure, the main loss sources are switching devices and magnetic components. Based on the simplified circuit model and the effective value function expression of the inductor current derived in step 1, the fundamental wave analysis method, Dowell equation, and improved generalized Steinmetz formula are used to establish a comprehensive DC power converter loss calculation model;
[0011] Step 3: According to the DC power converter loss calculation model established in step 2, analyze the key factors affecting the operating performance of the DC power converter, and determine the optimization objectives and constraints in combination with the transmission power function expression derived in step 1;
[0012] Step 4: Use Python 3.8 to call the Gurobi solver to calculate the optimal control strategy of the DC power converter under the specified transmission power.
[0013] In step 1, the input and output voltage waveforms of the DC power converter under the triple phase shift control mode are square waves, and the phase difference is determined by the control strategy. The corresponding current waveform is a trapezoidal waveform, which is affected by the comprehensive influence of the input and output voltages, load and phase difference. The DC power converter can be equivalent to a simplified circuit model of two voltage sources connected in series with an inductor.
[0014] Since the DC power converter current is symmetrical, i L (t) = -i L (t+T / 2), we only need to find the expression of the current in the first half of the cycle. L (t) is the current amplitude at time t; T is the period;
[0015] The expression of the inductor current in the first half cycle is as follows:
[0016]
[0017] Where: i L (t 0 ) is the current inflection point t 0 The inductor current at the moment i L (t 1 ) is the current inflection point t 1 The inductor current at the moment i L (t 2 ) is the current inflection point t 2 The inductor current at the moment i L (t 3 ) is the current inflection point t 3 The inductor current at the moment i L (t 4 ) is the current inflection point t 4 The inductor current at the moment; k is the voltage transformation ratio, k = U dc1 / (nU dc2 );n is the transformer ratio;U dc1 is the DC voltage on the primary side of the DC power converter; U dc2 is the DC voltage on the secondary side of the DC power converter; D 1 D is the phase shift between the pulse signals of the switching devices on both sides of the high-frequency transformer in the converter; 2is the phase shift between the pulse signals of the primary switching devices; D 3 is the phase shift between the pulse signals of the secondary side switching devices; f is the frequency; L is the inductance.
[0018] Ideally, the function expression of transmission power P is:
[0019]
[0020] In the step 2,
[0021] (1): The switching device loss expression is as follows:
[0022] P 1 =P CON +P SW
[0023] Where P 1 is the total loss of the switching device; P CON is the conduction loss of the switching device; P SW is the switching loss of the switching device
[0024] Among them, the conduction loss P con and switching loss P SW The expression is as follows:
[0025]
[0026] P SW =ft off [(U dc1 +V F )(|i L (t0)|+|i L (t 1 )|)+n(U dc2 +V F )(|i L (t 3 )|+|i L (t 4 )|)]
[0027] Where V DS is the conduction voltage drop of the transistor; V F is the conduction voltage drop of the freewheeling diode; t off is the turn-off time; n is the transformer ratio; t 0 ,t 1 ,t 2 ,t 3 ,t 4 ,t 5 These are the six inflection points of the current in the first half cycle.
[0028] (2): The expression of high frequency transformer loss in magnetic components is as follows:
[0029] P 2 =P cu-2 +P core-2
[0030] Where P 2 is the total loss of the high-frequency transformer; P cu-2 is the transformer winding loss; P core-2 is the transformer core loss.
[0031] Among them, the transformer winding loss P cu-2 The expression is as follows:
[0032]
[0033] Where: is the AC resistance coefficient of the hth harmonic of the primary winding of the transformer; is the AC resistance coefficient of the hth harmonic of the transformer secondary winding; R dc_pri is the DC resistance of the primary winding of the transformer; R dc_sec is the DC resistance of the secondary winding of the transformer; N is the highest order of summation; is the inductor current amplitude of the hth harmonic; F R (h) is the AC resistivity under the hth harmonic; △ is the normalized thickness of the solid round wire winding; m is the number of winding layers; d r is the diameter of the solid circular conductor; σ w is the electrical conductivity of copper; μ 0 is the vacuum magnetic permeability; N t H is the number of turns of a single-layer round conductor; w is the core window height; and They are and The transient expression of and They are the primary voltage u of the high-frequency transformer ab and the secondary voltage nu returned to the primary side cd The hth harmonic component; ω is the angular frequency; h is the harmonic order.
[0034] (3): The transformer core loss expression is as follows:
[0035]
[0036] In the formula, △B is the peak-to-peak value of magnetic flux density; B m_pri B is the peak value of primary magnetic flux density of high-frequency transformer; m_sec is the peak value of the secondary magnetic flux density of the high-frequency transformer; α, β, Cm is the loss coefficient.
[0037] (4): The expression of inductance loss in magnetic components is as follows:
[0038] P 3 =P cu-3 +P core-3
[0039] Where P 3 is the total inductor loss; P cu-3 is the inductor winding loss; P core-3 is the inductor core loss.
[0040] Among them, the expression of inductor winding loss is as follows:
[0041]
[0042] In the formula, I rms is the effective value of current; R dc is the DC resistance.
[0043] The expression of inductor core loss is as follows:
[0044]
[0045] In the formula, C m , α and β are loss coefficients; B is the magnetic flux density; (B j ,t j ) is the jth inflection point of the piecewise linear magnetic flux density waveform; B j is the magnetic flux density at the jth inflection point; B j+1 is the magnetic flux density at the j+1th inflection point; t j is the moment of the j-th inflection point;
[0046] t j+1 is the moment of the j+1th inflection point; θ is radians.
[0047] (5): Total loss of DC power converter P total The expression is:
[0048] P total =P 1 +P 2 +P 3
[0049] Where P 1 is the total loss of the switching device; P 2 is the total loss of the high-frequency transformer; P 3 is the total inductor loss.
[0050] In step 3, it can be seen from the loss model established in step 2 that the magnetic component winding loss is proportional to the current. Taking the minimum loss as the optimization goal, the objective function is established as:
[0051] min(P 1 +P 2 +P 3 )
[0052] Power balance constraints:
[0053] P=Pon
[0054] Where P on The specified transmission power.
[0055] Soft switching constraints:
[0056]
[0057] In step 4, a mixed integer linear programming optimal phase-shift control model including an objective function, power balance constraints, and soft switch constraints is established. The optimal phase-shift control model is solved by calling the Gurobi solver in Python 3.8 to obtain D 1 , D 2 , D 3 .
[0058] The present invention provides a triple phase shift optimization control method for a DC power converter with integrated source, grid, load and storage, and the technical effects are as follows:
[0059] 1) The present invention can be used to optimize the triple phase shift control strategy of a DC power converter, thereby reducing converter losses and improving converter efficiency while ensuring zero voltage switching of switching devices.
[0060] 2) The present invention only needs to use a small amount of operating parameters of the DC power converter, such as frequency, inductor current, phase shift, etc., to accurately calculate the loss of the DC power converter, thereby facilitating practical engineering applications.
[0061] 3) Based on the triple phase-shift control method and combined with a comprehensive loss model, the present invention conducts an in-depth study on the control strategy of the DC power converter, which can significantly improve the reliability and performance of the DC power converter system, and is of great significance for its application in efficient energy conversion. BRIEF DESCRIPTION OF THE DRAWINGS
[0062] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:
[0063] Figure 1 This is the topological structure diagram of the DC power converter.
[0064] Figure 2 This is the waveform diagram of the DC power converter under triple phase-shift control.
[0065] Figure 3 Simplified circuit model for DC power converter.
[0066] Figure 4 This is a diagram showing the loss structure of a DC power converter.
[0067] Figure 5 The figure is a calculation flow chart of the present invention.
[0068] Figure 6 This is the measurement result diagram of the traditional single-phase shifted waveform of the DC power converter.
[0069] Figure 7 This is the waveform measurement result diagram after the phase shift control of the DC power converter is optimized. DETAILED DESCRIPTION
[0070] A triple phase shift optimization control method for a DC power converter integrated with source, grid, load and storage comprises the following steps:
[0071] Step 1: Analyze the working waveform characteristics of the DC power converter under the triple phase shift control mode, and derive the simplified circuit model and the functional expressions of the inductor current and the transmission power;
[0072] Step 2: In the DC power converter structure, the main loss sources are switching devices and magnetic components. Based on the simplified circuit model and current effective value expression derived in step 1, a comprehensive DC power converter loss calculation model is established using the fundamental wave analysis method, the Dowe11 equation, and the improved generalized Steinmetz formula;
[0073] Step 3: According to the loss calculation model established in step 2, analyze the key factors affecting the operating performance of the DC power converter, and determine the optimization objectives and constraints in combination with the transmission power expression derived in step 1;
[0074] Step 4: Use Python 3.8 to call the Gugbi,solver to calculate the optimal control strategy of the DC power converter under the,specified transmission power.
[0075] Through the above steps 1 to 4, the triple phase-shift optimal control strategy of the DC power converter considering the loss model is realized.
[0076] In step 1, the DC power converter topology is as follows: Figure 1 As shown in the figure, the working waveform characteristics of the DC power converter under the triple phase shift control mode are as follows Figure 2 As shown, the equivalent circuit model is as follows Figure 3 shown.
[0077] Since the inductor current has a symmetrical upper and lower half-wave characteristic when the DC power converter reaches a steady state, only the inductor current in the first half cycle is analyzed. L (t) is the expression of the inductor current at the inflection point of the current waveform. In the first half of the cycle, the inductor current exists at t 0 ,t 1 ,t 2 ,t 3 ,t 4 Five waveform inflection points.
[0078]
[0079] Where: k is the voltage transformation ratio, k = U dc1 / (nU dc2 );n is the transformer ratio;U dc1 is the DC voltage on the primary side of the DC power converter; U dc2 is the DC voltage on the secondary side of the DC power converter; D 1 D is the phase shift between the pulse signals of the switching devices on both sides of the high-frequency transformer in the converter; 2 is the phase shift between the pulse signals of the primary switching devices; D 3 is the phase shift between the pulse signals of the secondary side switching devices; f is the frequency; L is the inductance.
[0080] Ideally, the transmission power is
[0081]
[0082] In step 2, the DC power converter loss is composed as follows: Figure 4 shown.
[0083] according to Figure 3 By simplifying the circuit model and the inductor current expression, the switching device loss expression is derived as follows:
[0084] P 1 =P CON +P SW
[0085] Where P 1 is the total loss of the switching device; P CON is the conduction loss of the switching device; P SW is the switching loss of the switching device.
[0086] Among them, the expressions of conduction loss and switching loss are as follows:
[0087]
[0088] Where VDS is the conduction voltage drop of the transistor; V F is the conduction voltage drop of the freewheeling diode; t off is the off time.
[0089] The fundamental wave analysis method, Dowe11 equation and improved generalized Steinmetz formula are used to derive the loss expression of high frequency transformer in magnetic components as follows:
[0090] P 2 =P cu-2 +P core-2
[0091] Where P 2 is the total loss of the high-frequency transformer; P cu-2 is the transformer winding loss; P core-2 is the transformer core loss.
[0092] The transformer winding loss expression is as follows:
[0093]
[0094] Where: is the AC resistance coefficient of the hth harmonic of the primary winding of the transformer; is the AC resistance coefficient of the hth harmonic of the transformer secondary winding; R dc_pri is the DC resistance of the primary winding of the transformer; R dc_sec is the DC resistance of the secondary winding of the transformer. N is the highest order of summation; is the inductor current amplitude of the hth harmonic; Δ is the normalized thickness of the solid circular wire winding; m is the number of winding layers; d r is the diameter of the solid circular conductor; σ w is the electrical conductivity of copper; μ 0 is the vacuum magnetic permeability; N t H is the number of turns of a single-layer round conductor; w is the core window height, and They are the primary voltage u of the high-frequency transformer ab and the secondary voltage nu returned to the primary side cd The hth harmonic component; U ab and U cd are the transformer primary and secondary AC voltages u ab 、u cd The DC amplitude of ω; ω is the angular frequency.
[0095] The transformer core loss expression is as follows:
[0096]
[0097] In the formula, ΔB is the peak-to-peak value of magnetic flux density; B m_pri B is the peak value of primary magnetic flux density of high-frequency transformer; m_sec is the peak value of the secondary magnetic density of the high-frequency transformer.
[0098] The expression for inductance loss in magnetic components is as follows:
[0099] P 3 =P cu-3 +P core-3
[0100] Where P 3 is the total loss of the high-frequency transformer; P cu-3 is the inductor winding loss; P core-3 is the inductor core loss.
[0101] Among them, the expression of inductor winding loss is as follows:
[0102]
[0103] In the formula, I rms is the effective value of current.
[0104] The expression of inductor core loss is as follows:
[0105]
[0106] In the formula, C m , α and β are loss coefficients; B is the magnetic flux density; (B j ,t j ) is the jth inflection point of the piecewise linear magnetic flux density waveform.
[0107] The total loss of the DC power converter is:
[0108] P total =P 1 +P 2 +P 3 .
[0109] In step 3, it can be seen from the loss model established in step 2 that the magnetic component winding loss is proportional to the current. Taking the minimum loss as the optimization goal, the objective function is established as:
[0110] min(P 1 +P 2 +P 3 )
[0111] Power balance constraints:
[0112] P=Pon
[0113] Where P on The specified transmission power.
[0114] Soft switching constraints:
[0115]
[0116] In step 4, a mixed integer linear programming optimal phase-shift control model including an objective function, power balance constraints, and soft switch constraints is established. The optimal phase-shift control model is solved by calling the Gurobi solver in Python 3.8 to obtain D 1 , D 2 , D 3 .
[0117] Example:
[0118] Step 1: Analyze the working waveform characteristics of the DC power converter under the triple phase shift control mode, and derive the simplified circuit model and the functional expressions of the inductor current and transmission power:
[0119] Figure 1 is the topology of the DC power converter. The DC voltage on the input and output sides is U dc1 , U dc2 ; Four switching devices are used to form an H-type full-bridge structure; a high-frequency transformer with a transformation ratio of n:1 and an inductor L are connected between the two full bridges, and the size of the inductor is equal to the sum of the external inductor connected in series in the circuit and the leakage inductance of the high-frequency transformer. Under the triple phase-shift control mode, the excitation voltage waveform at both ends of the DC power converter is a step wave with different duty cycles. Figure 2 As shown, in the triple phase shift control mode, D 1 D is the phase shift between the pulse signals of the switching devices on both sides of the high-frequency transformer in the converter; 2 is the phase shift between the pulse signals of the primary switching devices; D 3 It is the phase shift between the pulse signals of the secondary side switching devices.
[0120] based on Figure 1 As shown in the DAB converter topology, since the magnetizing inductance is much larger than the leakage inductance, the following can be obtained: Figure 3 The simplified circuit model of the DAB converter is shown.
[0121] Since the inductor current has a symmetrical characteristic of the upper and lower half waves when the DC power converter reaches a steady state, only the inductor current in the first half cycle is analyzed. The current expression is as follows:
[0122]
[0123] Where, T hs is half a cycle, k is the voltage transformation ratio, k==U dc1 / (nUdc2 );n is the transformer ratio;U dc1 is the DC voltage on the primary side of the DC power converter; U dc2 is the DC voltage on the secondary side of the DC power converter; D 1 D is the phase shift between the pulse signals of the switching devices on both sides of the high-frequency transformer in the converter; 2 is the phase shift between the pulse signals of the primary switching devices; D 3 is the phase shift between the pulse signals of the secondary side switching devices; f is the frequency; L is the inductance.
[0124] Without considering power loss, the ideal transmission power is:
[0125]
[0126] Step 2: DC power converter loss model:
[0127] The loss structure of DC power converter is as follows: Figure 4 shown.
[0128] according to Figure 2 The operating characteristics of the DC power converter and the current expression in equation (1) derive the switching device loss expression as follows:
[0129] P 1 =P CON +P SW (3);
[0130] Where P 1 is the total loss of the switching device; P CON is the conduction loss of the switching device; P SW is the switching loss of the switching device.
[0131] Among them, the expressions of conduction loss and switching loss are as follows:
[0132]
[0133] P SW =ft off [(U dc1 +V F )(|i L (t 0 )|+|i L (t 1 )|)+n(U dc2 +V F )(|i L (t 3 )|+|i L (t 4 )|)] (5);
[0134] Where V DS is the conduction voltage drop of the transistor; V F is the conduction voltage drop of the freewheeling diode; t off is the off time.
[0135] Combination Figure 3 The simplified circuit diagram in is used to obtain the expression of magnetic component loss by using the fundamental wave analysis method, Dowe11 equation and improved generalized Steinmetz formula.
[0136] The expression for high-frequency transformer loss in magnetic components is as follows:
[0137] P 2 =P cu-2 +P core-2 (6);
[0138] Where P 2 is the total loss of the high-frequency transformer; P cu-2 is the transformer winding loss; P core-2 is the transformer core loss.
[0139] The expression of winding transformer resistance loss is as follows:
[0140]
[0141] Where: is the AC resistance coefficient of the hth harmonic of the primary winding of the transformer; is the AC resistance coefficient of the hth harmonic of the transformer secondary winding; R dc_pri is the DC resistance of the primary winding of the transformer; R dc_sec is the DC resistance of the secondary winding of the transformer. N is the highest order of summation; is the inductor current amplitude of the hth harmonic; Δ is the normalized thickness of the solid circular wire winding; m is the number of winding layers; d r is the diameter of the solid circular conductor; σ w is the electrical conductivity of copper; μ 0 is the vacuum magnetic permeability; N t H is the number of turns of a single-layer round conductor; w is the core window height, and They are the primary voltage u of the high-frequency transformer ab and the secondary voltage nu returned to the primary side cd The hth harmonic component; U ab and U cd are the transformer primary and secondary AC voltages u ab 、u cd The DC amplitude of ω; ω is the angular frequency.
[0142] The transformer core loss expression is as follows:
[0143]
[0144] In the formula, △B is the peak-to-peak value of magnetic flux density; B m_pri B is the peak value of primary magnetic flux density of high-frequency transformer; m_sec is the peak value of the secondary magnetic density of the high-frequency transformer.
[0145] The expression for inductance loss in magnetic components is as follows:
[0146] P 3 =P cu-3 +P core-3 (9);
[0147] Where P 3 is the total inductor loss; P cu-3 is the inductor winding loss; P core-3 is the inductor core loss.
[0148] Among them, the expression of inductor winding loss is as follows:
[0149]
[0150] In the formula, I rms is the effective value of current.
[0151] The expression of inductor core loss is as follows:
[0152]
[0153] In the formula, C m , α and β are loss coefficients; B is the magnetic flux density; (B j ,t j ) is the jth inflection point of the piecewise linear magnetic flux density waveform.
[0154] Step 3: Determine the optimization objectives and constraints:
[0155] From the loss model established in step 2, it can be seen that the magnetic component winding loss is proportional to the current. Taking the minimum loss as the optimization goal, the objective function is established as:
[0156] min(P 1 +P 2 +P 3 )(12); Power balance constraints:
[0157] P = Pon (13);
[0158] Where P on The specified transmission power.
[0159] Soft switching constraints:
[0160]
[0161] Step 4: Call the solver to solve:
[0162] The optimal phase-shift control model established in step 3 is a mixed integer linear programming model. The established model is solved by calling the Gurobi solver in Python 3.8 to obtain D 1 , D 2 , D 3 .
[0163] Step 5: Based on the expressions given in steps 1 to 4 above, the calculation process of the triple phase shift optimal control strategy of the DC power converter considering the loss model is established, such as Figure 5 shown.
[0164] By comparing and analyzing this scheme with the traditional SPS control scheme, the optimization effect of this scheme on the operating performance of the DC power converter is verified. Using TMS320F28335 as the main control chip and C3M0075120K SiC MOSFET as the switching device, a 24V / 100V, 20kHz DC power converter experimental prototype is built.
[0165] Figure 6 This is the measurement result of the traditional single-phase shift waveform of the DC power converter. At this time, the transmission power per unit value P* is about 0.32, the voltage conversion ratio k=4.17, the current stress is about 5.8A, and the overall loss is 11.124w.
[0166] Figure 7 The waveform measurement result diagram of the DC power converter after phase shift control optimization. At this time, the transmission power per unit value P* is about 0.32, the voltage conversion ratio k=4.17, the current stress is about 5.0A, and the overall loss is 7.812w. It can be obtained that when the transmission power is consistent, the overall loss and current stress under this control scheme are significantly reduced compared with the traditional single phase shift control method.
[0167] The method of the present invention is particularly suitable for reducing converter losses and improving the performance and stability of the overall system of the DC power converter under a specified transmission power. Because the present invention is aimed at the power electronic topology of the DC power converter and the steady-state voltage waveform under the triple phase shift control mode, a triple phase shift optimization control method for the DC power converter considering the loss model is obtained. The present invention can realize the triple phase shift optimization control of the DC power converter, ensuring that the efficiency of the DC power converter is effectively improved under the specified transmission power.
[0168] Based on the loss fine model of DC power converter and the triple phase shift control method, the present invention proposes a triple phase shift optimization control method for DC power converter considering the loss model, which is used to solve the triple phase shift optimal control of DC power converter under the specified transmission power. According to the simplified circuit model and the working waveform characteristics under the triple phase shift control mode, the function expression of inductor current and transmission power is derived. The fundamental wave analysis method, Dowell equation and improved generalized Steinmetz formula are respectively used to establish a comprehensive DC power converter loss calculation model. According to the established loss calculation model, combined with the transmission power expression, the optimization target and constraint conditions are determined, and Python 3.8 is used to call the Gurobi solver to calculate the optimal control strategy of the DC power converter under the specified transmission power. The scheme is experimentally compared and analyzed with the traditional SPS control scheme. The experimental results show that the proposed method can effectively improve the efficiency of the DC power converter.
Claims
1. A triple phase-shift optimization control method for DC power converters with integrated source, grid, load and storage, characterized in that The following steps are involved: Step 1: Analyze the working waveform characteristics of the DC power converter under the triple phase shift control mode, and derive the simplified circuit model and the inductor current and transmission power function expressions; Step 2: In the DC power converter structure, the loss sources are switching devices and magnetic components; according to the simplified circuit model and the inductor current effective value function expression derived in step 1, a DC power converter loss calculation model is established; Step 3: According to the DC power converter loss calculation model established in step 2, analyze the key factors affecting the operating performance of the DC power converter, and determine the optimization objectives and constraints in combination with the transmission power function expression derived in step 1; Step 4: Calculate the optimal control strategy of the DC power converter under the specified transmission power.
2. According to the triple phase shift optimization control method for DC power converter with source-grid-load-storage integration as claimed in claim 1, Features: In step 1, the input and output voltage waveforms of the DC power converter under the triple phase-shift control mode are square waves, and the phase difference is determined by the control strategy; the corresponding current waveform is a trapezoidal waveform, which is affected by the comprehensive influence of the input and output voltages, load and phase difference; the DC power converter can be equivalent to a simplified circuit model of two voltage sources connected in series with an inductor.
3. According to the triple phase shift optimization control method for DC power converter with source-grid-load-storage integration as claimed in claim 2, Features: Since the DC power converter current is symmetrical, i L (t) = -i L (t+T / 2), we only need to find the expression of the current in the first half of the cycle; i L (t) is the current amplitude at time t; T is the period; The expression of the inductor current in the first half cycle is as follows: Where: i L (t0) is the inductor current at the current inflection point t0; i L (t1) is the inductor current at the current inflection point t1; i L (t2) is the inductor current at the current inflection point t2; i L (t3) is the inductor current at the current inflection point t3; i L (t4) is the inductor current at the current inflection point t4; k is the voltage transformation ratio, k = U dc1 / (nU dc2 );n is the transformer ratio;U dc1 is the DC voltage on the primary side of the DC power converter; U dc2 is the DC voltage on the secondary side of the DC power converter; D1 is the phase shift between the pulse signals of the switch devices on both sides of the high-frequency transformer in the converter; D2 is the phase shift between the pulse signals of the switch devices on the primary side; D3 is the phase shift between the pulse signals of the switch devices on the secondary side; f is the frequency; L is the inductance; The function expression of transmission power P is:
4. According to the triple phase shift optimization control method for DC power converter with source-grid-load-storage integration as claimed in claim 1, Features: In the step 2, (1): The switching device loss expression is as follows: P1=P CON +P SW Where P1 is the total loss of the switching device; P CON is the conduction loss of the switching device; P SW is the switching loss of the switching device Among them, the conduction loss P con and switching loss P SW The expression is as follows: P SW =ft off [(U dc1 +V F )(|i L (t0)|+|i L (t1)|)+n(U dc2 +V F )(|i L (t3)|+|i L (t4)|)] Where V DS is the conduction voltage drop of the transistor; V F is the conduction voltage drop of the freewheeling diode; t off is the turn-off time; n is the transformer ratio; t0, t1, t2, t3, t4, t5 are the six inflection points of the current in the first half cycle; (2): The expression of high-frequency transformer loss in magnetic components is as follows: P2=P cu-2 +P core-2 Where, P2 is the total loss of the high-frequency transformer; P cu-2 is the transformer winding loss; P core-2 is the transformer core loss; Among them, the transformer winding loss P cu-2 The expression is as follows: Where: is the AC resistance coefficient of the hth harmonic of the primary winding of the transformer; is the AC resistance coefficient of the hth harmonic of the secondary winding of the transformer; R dc_pri is the DC resistance of the primary winding of the transformer; R dc_sec is the DC resistance of the secondary winding of the transformer; N is the highest order of summation; is the inductor current amplitude of the hth harmonic; F R (h) is the AC resistivity under the hth harmonic; △ is the normalized thickness of the solid round wire winding; m is the number of winding layers; d r is the diameter of the solid circular conductor; σ w is the electrical conductivity of copper; μ0 is the magnetic permeability of vacuum; N t H is the number of turns of a single-layer round conductor; w is the core window height; and They are and The transient expression of and They are the primary voltage u of the high-frequency transformer ab and the secondary voltage nu returned to the primary side cd The hth harmonic component; ω is the angular frequency; h is the harmonic order; (3): The transformer core loss expression is as follows: In the formula, △B is the peak-to-peak value of magnetic flux density; B m_pri B is the peak value of primary magnetic flux density of high-frequency transformer; m_sec is the peak value of the secondary magnetic flux density of the high-frequency transformer; α, β, C m is the loss coefficient; (4): The expression of inductance loss in magnetic components is as follows: P3=P cu-3 +P core-3 Where, P3 is the total inductor loss; P cu-3 is the inductor winding loss; P core-3 is the inductor core loss; Among them, the expression of inductor winding loss is as follows: In the formula, I rms is the effective value of current; R dc is the DC resistance; The expression of inductor core loss is as follows: In the formula, C m , α and β are loss coefficients; B is the magnetic flux density; (B j ,t j ) is the jth inflection point of the piecewise linear magnetic flux density waveform; B j is the magnetic flux density at the jth inflection point; B j+1 is the magnetic flux density at the j+1th inflection point; t j is the moment of the j-th inflection point; t j+1 is the moment of the j+1th inflection point; θ is radians; (5): Total loss of DC power converter P total The expression is: P total =P1+P2+P3 Where, P1 is the total loss of the switching device; P2 is the total loss of the high-frequency transformer; P3 is the total inductor loss.
5. The triple phase shift optimization control method for DC power converters integrated with source, grid, load and storage according to claim 4 is characterized by: In step 3, it can be seen from the loss model established in step 2 that the magnetic element winding loss is proportional to the current; taking the minimum loss as the optimization goal, the objective function is established as: min(P1+P2+P3) Power balance constraints: P=Pon Where P on is the specified transmission power; Soft switching constraints:
6. The triple phase shift optimization control method for DC power converters integrated with source, grid, load and storage according to claim 5 is characterized by: In the step 4, a mixed integer linear programming optimal phase-shift control model including an objective function, a power balance constraint, and a soft switch constraint is established; the established optimal phase-shift control model is solved by calling the Gurobi solver using Python 3.8 to obtain D1, D2, and D3 in the triple phase-shift control mode, respectively.