Power allocation method for single-stage multi-port optical storage system with ripple suppression function

Abstract

The present invention discloses a single-stage multi-port optical storage system power distribution method with ripple suppression function, which generates a zero-sequence component v with the ability to regulate power distribution based on the port power of the current power frequency cycle. zs1 In addition, based on the port power of the previous power frequency cycle, an iterative learning strategy is used to generate a zero-sequence component v that has the effect of suppressing port power ripple zs2 ; Then inject the zero sequence component v into the original three-phase modulated signal zs1 and v zs2 , and obtain the final three-phase modulation signal. Finally, the three-phase modulation signal is compared with the asymmetric triangular carrier to generate a switching signal to realize the bridge arm action of the photovoltaic storage power generation system.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic power generation, and more specifically, relates to a power distribution method for a single-stage multi-port photovoltaic storage system with a ripple suppression function. Background Art

[0002] Photovoltaic power generation is a technological means of alleviating fossil energy shortages and environmental pollution. However, due to factors such as ambient temperature and sunlight, photovoltaic power generation is significantly intermittent and unpredictable. Photovoltaic power generation systems with integrated energy storage are considered an effective solution to these challenges, improving power quality and providing a more stable power supply to the grid.

[0003] Among the many PV-plus-storage power generation system topologies, PV-plus-storage power generation systems based on single-stage multi-port inverters eliminate the need for additional DC power converters. Instead, they interconnect multiple DC ports with one AC port within a single power conversion stage, offering significant advantages such as high conversion efficiency, high power density, and low hardware cost. Such systems are also known as single-stage multi-port PV-plus-storage systems.

[0004] In single-stage, multi-port solar-to-storage systems, achieving power distribution between different DC ports is a major challenge. Existing solutions use additional PI controllers to adjust redundant vectors in the vector space to achieve power distribution between DC ports. However, this strategy requires the design of a complex space vector modulation algorithm, resulting in unsatisfactory control and large DC port power ripple. Therefore, there is an urgent need to develop a power distribution method for single-stage, multi-port solar-to-storage systems that does not require a complex modulation algorithm, ensures optimal control, and avoids large DC port power ripple. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a single-stage multi-port photovoltaic storage system power distribution method with ripple suppression function. The method realizes power distribution between DC ports by directly adjusting the system zero-sequence component, thereby avoiding the complex space vector modulation algorithm design. At the same time, the present invention adopts an iterative learning strategy to compensate for the zero-sequence component, thereby achieving effective suppression of DC port power ripple.

[0006] To achieve the above-mentioned object of the invention, the present invention provides a single-stage multi-port optical storage system power distribution method with ripple suppression function, characterized by comprising the following steps:

[0007] (1) Based on the DC port power of the current power frequency cycle, a zero-sequence component v is generated that has the ability to regulate the power distribution between DC ports. zs1,k , k is the power frequency cycle number;

[0008] (2) Based on the DC port power of the previous power frequency cycle, an iterative learning strategy is used to generate a zero-sequence component v that has the effect of suppressing the DC port power ripple. zs2,k ;

[0009] (3) Inject the zero-sequence component v mentioned above into the original three-phase modulated signal, which respectively plays the role of regulating power distribution and suppressing DC port power ripple. zs1 and zero sequence component v zs2 , get the final three-phase modulated signal;

[0010] (4) Comparing the final three-phase modulated signal with the asymmetric triangular carrier to generate a digital switching signal for driving the single-stage multi-port optical storage system;

[0011] (5) Use digital switch signals to control the action of the switch tubes on the three-phase bridge arm in the single-stage multi-port photovoltaic storage system to achieve the regulation of the grid side voltage of the single-stage multi-port photovoltaic storage system.

[0012] The object of the invention of the present invention is achieved like this:

[0013] The present invention provides a single-stage multi-port optical storage system power distribution method with ripple suppression function, which generates a zero-sequence component v with the ability to regulate power distribution based on the port power of the current power frequency cycle. zs1 In addition, based on the port power of the previous power frequency cycle, an iterative learning strategy is used to generate a zero-sequence component v that has the effect of suppressing port power ripple zs2 ; Then inject the zero sequence component v into the original three-phase modulated signal zs1 and v zs2 , and obtain the final three-phase modulation signal. Finally, the three-phase modulation signal is compared with the asymmetric triangular carrier to generate a switching signal to realize the bridge arm action of the photovoltaic storage power generation system.

[0014] At the same time, the single-stage multi-port optical storage system power distribution method with ripple suppression function of the present invention also has the following beneficial effects:

[0015] (1) The topology of the photovoltaic power generation system adopts a single-stage multi-port inverter structure instead of the two-stage structure used in traditional solutions. Therefore, it can eliminate the additional DC power converter and the multi-stage power flow path introduced by it, thereby enhancing the energy transmission efficiency and improving the overall power density of the photovoltaic power generation system.

[0016] (2) The technical solution adopted by the present invention does not require a complex space vector modulation algorithm. It can achieve power distribution between DC ports through a simple carrier modulation algorithm and effectively suppress the generation of DC port power ripple. It solves the technical problem that the traditional power distribution method relies on a complex space vector modulation algorithm and the DC port power ripple is large. Therefore, the method of the present invention also has the advantages of simple control process and easy implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of a power distribution method for a single-stage multi-port optical storage system with ripple suppression function according to the present invention;

[0018] Figure 2 This is the topological structure diagram of a single-stage multi-port optical storage system;

[0019] Figure 3 This is the working condition of the single-stage multi-port optical storage system under three different port voltage conditions;

[0020] Figure 4 This is the working condition of the single-stage multi-port optical storage system under three different port power distribution situations;

[0021] Figure 5 This is a comparison chart of the power ripple performance of a single-stage multi-port optical storage system achieved using a traditional method and a method of the present invention. DETAILED DESCRIPTION

[0022] The following describes the specific embodiments of the present invention in conjunction with the accompanying drawings so that those skilled in the art can better understand the present invention. It should be noted that in the following description, when detailed descriptions of known functions and designs may dilute the main content of the present invention, such descriptions will be omitted here.

[0023] Example

[0024] In this embodiment, a single-stage multi-port optical storage system is first introduced. Figure 2 As shown, the hardware circuit includes DC bus voltage stabilizing capacitors C1 and C2, diode D, LC filter, converter three-phase bridge arm and its switch tube S x1 、S x2 、S x3 、S x4 , where x can represent any of the three phases a, b, and c. In terms of topology, it has one AC output port and two DC output ports. The DC port connected to photovoltaic power generation is called the upper port, and the DC port connected to energy storage is called the lower port.

[0025] The following combination Figure 2, the power distribution method of the single-stage multi-port optical storage system with ripple suppression function of the present invention is described in detail, such as Figure 1 As shown, the following steps are included:

[0026] S1: Based on the current power frequency cycle T k The DC port power generates a zero-sequence component v that has the ability to regulate the power distribution between DC ports. zs1,k ;

[0027] S1.1: Monitor the operating status of the photovoltaic unit and energy storage device through the power management module of the photovoltaic power generation system, and set the reference power P of the upper port connected to the photovoltaic unit. href ;

[0028] S1.2: Obtain the three-phase current i through the grid-side current sensor sampling a 、i b 、i c And combine it with the duty cycle of the three-phase bridge arm switch tube to get the current power frequency period T k The upper port power P h,k , the operation relationship is as follows:

[0029] P h,k =V h (d a1 i a +d b1 i b +d c1 i c )

[0030] Among them, d a1 d b1 d c1 They represent the first switch tube S of the three-phase bridge arm of the single-stage multi-port optical storage system. a1 、S b1 、S c1 The duty cycle, V h 、V l Represent the voltages of the upper and lower ports respectively;

[0031] S1.3: Based on the upper port power P obtained above h,k And the upper port reference power P href The current power frequency period T is obtained by difference calculation k Upper port power error Δ P h,k , the operation relationship is as follows:

[0032] Δ P h,k =P href -P h,k

[0033] S1.4: According to the upper port power error Δ P h,k Generates zero-sequence component v with the ability to regulate power distribution between DC ports zs1,k , the operation relationship is as follows:

[0034] v zs1,k =k 1Δ P h,k

[0035] Wherein, k1 represents the feedback adjustment coefficient.

[0036] The topology of the single-stage multi-port photovoltaic storage system belongs to the inverter. The zero-sequence component is an additional control degree of freedom in the inverter bridge structure. Adjusting the zero-sequence component will not affect the three-phase composite voltage output on the grid side, and adjusting the zero-sequence component can achieve power distribution between DC ports.

[0037] S2: Based on the previous power frequency cycle T k-1 The DC port power is calculated by using an iterative learning strategy to generate a zero-sequence component v that can suppress the DC port power ripple. zs2,k .

[0038] S2.1: Extract the last power frequency period T k-1 The injected zero sequence component is recorded as v zs2,k-1 If the current power frequency cycle is the starting power frequency cycle, it is initialized as follows:

[0039] v zs2,k-1 =0

[0040] S2.2: According to the last power frequency cycle T k-1 The historical port power P at the same sampling time h,k-1 Compared with the above upper port reference power P href Subtract and get the historical port power error Δ P h,k-1 , the operation relationship is as follows:

[0041] Δ P h,k-1 =P href -P h,k-1

[0042] S2.3: Based on historical port power errors Δ P h,k-1 , an iterative learning strategy is used to generate a zero-sequence component v that can suppress port power ripple. zs2,k , the operation relationship is as follows:

[0043] v zs2,k =v zs2,k-1 +k 2Δ Ph,k-1

[0044] Among them, k2 represents the iterative learning strategy adjustment coefficient.

[0045] The DC port power distribution of the single-stage multi-port optical storage system has a switching control feature, based on the previous power frequency cycle T k-1 The DC port power information is used to compensate the current power frequency period T using an iterative learning strategy. k The zero-sequence component is reduced to avoid unsatisfactory power distribution due to switching control characteristics, which may cause large DC port power ripple.

[0046] S3: Inject the zero-sequence component v mentioned above into the original three-phase modulated signal to regulate power distribution and suppress DC port power ripple. zs1,k and zero sequence component v zs2,k , and obtain the final three-phase modulated signal.

[0047] S3.1: Superimpose the zero-sequence components v above to regulate power distribution and suppress DC port power ripple. zs1,k and zero sequence component v zs2,k , get the current power frequency period T k The zero sequence component v to be injected zs,k , the operation relationship is as follows:

[0048] v zs,k =v zs1,k +v zs2,k

[0049] S3.2: Limit the zero-sequence component to be injected to prevent it from causing the three-phase modulation signal to exceed the modulation range, and satisfy the following constraints:

[0050] -V h / 2-min(v ref )≤v zs,k ≤V h / 2-max(v ref )

[0051] Among them, v ref Represents the original three-phase modulated signal, min() and max() represent the minimum and maximum values ​​of the elements in the brackets.

[0052] S3.3: The zero-sequence component after the above limiting process Injected into the original three-phase modulated signal to obtain the final three-phase modulated signal

[0053]

[0054] By superimposing the above zero-sequence component on the three-phase modulated signal, the established power distribution target is achieved and the generation of DC port power ripple is effectively suppressed without affecting the regulation of the grid side voltage.

[0055] S4: Compare the obtained final three-phase modulated signal with the asymmetric triangular carrier to generate a digital switch signal for driving the single-stage multi-port optical storage system.

[0056] S4.1: Based on the current port voltage, an asymmetric carrier wave is generated with inconsistent amplitudes of the upper and lower carrier waves. The upper and lower carrier waves are both triangular waves with the same phase and frequency. The upper carrier wave is at V l -V h / 2~V h / 2, the lower carrier is -V h / 2~V l -V h Varies within the range of / 2.

[0057] S4.2: Compare the above final three-phase modulated signal with the asymmetric carrier to obtain the digital switching signal G x1 , G x2 , G x3 , G x4 , where x can represent any one of the three phases a, b, and c.

[0058] The upper and lower carrier amplitudes of the asymmetric triangular carrier change with the port voltage to adapt to the time-varying voltage of the upper and lower ports on the DC side, which provides feasibility for realizing port power distribution under the condition of unbalanced DC port voltage.

[0059] S5: Using digital switch signals to control the actions of the switches on the three-phase bridge arms of the single-stage multi-port solar-storage system, thereby adjusting the grid-side voltage of the single-stage multi-port solar-storage system;

[0060] In this embodiment, the digital switch signal G x1 Control switch tube S x1 The digital switch signal G x1 The complementary signal G x3 Control switch tube S x3 The digital switch signal G x2 Control switch tube S x2 The digital switch signal G x2 The complementary signal G x4 Control switch tube S x4 conduction.

[0061] Ultimately, a carrier-based modulation approach was employed to distribute power between DC ports, avoiding the complex design of a space vector modulation algorithm. Furthermore, an iterative learning strategy was employed to compensate for the zero-sequence component of the power distribution, effectively suppressing DC port power ripple.

[0062] Example verification

[0063] Assume the upper port voltage is V h =400V, the lower port voltage is V l =160~240V, the upper port reference power is P href =1000W, the rated voltage on the grid side is V n =110V, the rated power on the grid side is P gref =1000W.

[0064] like Figure 3 As shown, the steady-state performance of the photovoltaic power generation system at different port voltages is observed. Figure 3 (a) The voltage at the lower port is V l =240V, Figure 3 (b) The voltage at the lower port is V l =200V, Figure 3 (c) The voltage at the lower port is V l =160V. By observing the grid-side voltage and current waveforms and the total harmonic distortion (THD) indicator of the single-stage multi-port photovoltaic storage system, it can be seen that under the power allocation method proposed in this embodiment, the photovoltaic storage power generation system can operate stably under unbalanced port voltage conditions, and its operating status is not affected by changes in the port voltage.

[0065] like Figure 4 As shown in the figure, we observe the working conditions of the photovoltaic power generation system under three different port power distribution conditions. Among them, under the rated power condition of the grid side, Figure 4 (a) The upper port power reference is given as P href =800W, Figure 4 (b) The upper port power reference is given as P href =1000W, Figure 4 (c) The upper port power reference is given as P href =1200W. Observing the operating status of the single-stage multi-port solar-storage system and the DC port output power shows that the upper port output power can be adjusted according to the given port power reference value, and the voltage and current on the grid side remain stable and sinusoidal, indicating that the proposed method successfully achieves power distribution in a single-stage multi-port solar-storage system.

[0066] like Figure 5As shown, by observing the port power ripple performance of the traditional method and the method proposed in the present invention, it can be seen that the solution proposed in this embodiment has smaller port power ripple than the traditional solution, indicating that the method proposed in the present invention successfully achieves the suppression of port power ripple and has better control performance.

[0067] Although the above describes the illustrative specific embodiments of the present invention to facilitate understanding of the present invention by those skilled in the art, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concepts of the present invention are protected.

Claims

1. A single-stage multi-port optical storage system power distribution method with ripple suppression function, characterized in that: The following steps are involved: (1) Based on the DC port power of the current power frequency cycle, a zero-sequence component v is generated that has the ability to regulate the power distribution between DC ports. zs1,k , k is the power frequency cycle number; (1.1) The operating status of the photovoltaic unit and the energy storage device is monitored by the power management module of the photovoltaic power generation system, and the reference power P of the upper port connected to the photovoltaic unit is given. href ; (1.2) The three-phase current i is obtained by sampling the current sensor on the grid side. a 、i b 、i c And combine it with the duty cycle of the three-phase bridge arm switch tube to get the current power frequency period T k The upper port power P h,k : P h,k =V h (d a1 i a +d b1 i b +d c1 i c ) Among them, d a1 d b1 d c1 They represent the first switch tube S of the three-phase bridge arm of the single-stage multi-port optical storage system. a1 、S b1 、S c1 The duty cycle, V h 、V l Represent the voltages of the upper and lower ports respectively; (1.3), according to the upper port power P h,k And the upper port reference power P href The current power frequency period T is obtained by difference calculation k Upper port power error Δ P h,k : Δ P h,k =P href -P h,k (1.4), according to the upper port power error Δ P h,k Generates zero-sequence component v with the ability to regulate power distribution between DC ports zs1,k : v zs1,k =k 1Δ P h,k Among them, k1 represents the feedback adjustment coefficient; (2) Based on the DC port power of the previous power frequency cycle, an iterative learning strategy is used to generate a zero-sequence component v that has the effect of suppressing the DC port power ripple. zs2,k ; (2.1) Extract the previous power frequency period T k-1 The injected zero sequence component is recorded as v zs2,k-1 If the current power frequency cycle is the starting power frequency cycle, it is initialized as follows: v zs2,k-1 ＝0 (2.2), according to the previous power frequency cycle T k-1 The historical port power P at the same sampling time h,k-1 and the upper port reference power P href Subtract and get the historical port power error Δ P h,k-1 : Δ P h,k-1 =P href -P h,k-1 (2.3), based on the historical port power error Δ P h,k-1 , an iterative learning strategy is used to generate a zero-sequence component v that can suppress port power ripple. zs2,k : v zs2,k =v zs2,k-1 +k 2Δ P h,k-1 Among them, k2 represents the adjustment coefficient of the iterative learning strategy; (3) Inject the zero-sequence components v mentioned above into the original three-phase modulated signal to regulate the power distribution capability. zs1,k and the zero sequence component v that suppresses the DC port power ripple zs2,k , get the final three-phase modulated signal; (4) Comparing the final three-phase modulated signal with the asymmetric triangular carrier to generate a digital switching signal for driving the single-stage multi-port optical storage system; (5) Use digital switch signals to control the action of the switch tubes on the three-phase bridge arm in the single-stage multi-port photovoltaic storage system to achieve the regulation of the grid side voltage of the single-stage multi-port photovoltaic storage system.

2. The single-stage multi-port optical storage system power distribution method with ripple suppression function according to claim 1, characterized in that: The method for obtaining the final three-phase modulation signal in step (3) is: (3.1), the zero sequence component v zs1,k and zero sequence component v zs2,k The current power frequency period T is obtained by superposition k The zero sequence component v that needs to be injected zs,k : v zs,k =v zs1,k +v zs2,k (3.2), for the zero-sequence component v zs,k Perform the limiting process to satisfy the following constraints: -V h / 2-min(v ref )≤v zs,k ≤V h / 2-max(v ref ) Among them, v ref Represents the original three-phase modulated signal, min() and max() represent the minimum and maximum values ​​of the elements in the brackets; (3.3) The zero-sequence component after limiting Injected into the original three-phase modulated signal to obtain the final three-phase modulated signal 3. The single-stage multi-port optical storage system power distribution method with ripple suppression function according to claim 1, characterized in that: The method for generating the digital switch signal is: (4.1) Based on the current port voltage, an asymmetric carrier wave with inconsistent amplitudes of the upper and lower carrier waves is generated. The upper and lower carrier waves are both triangular waves with the same phase and frequency. The upper carrier wave is at V l -V h / 2~V h / 2 range, the download wave is -V h / 2~V l -V h Changes within the range of / 2; (4.2) will eventually get a three-phase modulated signal Compare with the asymmetric carrier to get the digital switching signal G x1 , G x2 , G x3 , G x4 , where x = a, b, c, representing any one of the three phases.

4. The single-stage multi-port optical storage system power distribution method with ripple suppression function according to claim 3, characterized in that: The operation process of the digital switch signal controlling the switch tubes on the three-phase bridge arm in the single-stage multi-port optical storage system is as follows: Using digital switch signal G x1 Control switch tube S x1 The digital switch signal G x1 The complementary signal G x3 Control switch tube S x3 The digital switch signal G x2 Control switch tube S x2 The digital switch signal G x2 The complementary signal G x4 Control switch tube S x4 conduction.

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