Single-stage multi-port optical storage system power distribution method with ripple suppression function

Abstract

The invention discloses a single-stage multi-port optical storage system power distribution method with a ripple suppression function, and the method comprises the steps: generating a zero-sequence component vzs1 with a power distribution regulation and control capability based on the port power of a current power frequency period; in addition, based on the port power of the previous power frequency period, a zero-sequence component vzs2 with a port power ripple suppression effect is generated by adopting an iterative learning strategy; the method comprises the following steps: firstly, generating an original three-phase modulation signal, then, injecting zero-sequence components vzs1 and vzs2 into the original three-phase modulation signal to obtain a final three-phase modulation signal, and finally, comparing the three-phase modulation signal with an asymmetric triangular carrier to generate a switching signal so as to realize the bridge arm action of the optical 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 technical means to alleviate the shortage of fossil energy and environmental pollution. However, affected by factors such as ambient temperature and light, photovoltaic power generation has significant intermittency and unpredictability. Photovoltaic power generation systems integrated with energy storage devices are considered to be an effective solution to the above problems. This system can improve power quality and provide a more stable power supply to the power grid.

[0003] Among the many photovoltaic storage power generation system topologies, the photovoltaic storage power generation system based on the single-stage multi-port inverter removes the additional DC power converter. It realizes the interconnection of multiple DC ports with one AC port in one power conversion stage, so it has the significant advantages of high conversion efficiency, high power density and low hardware cost. Such a system is also called a single-stage multi-port photovoltaic storage system.

[0004] In a single-stage multi-port photovoltaic storage system, how to achieve power distribution between different DC ports is a major challenge. The existing solution is to adjust the redundant vectors in the vector space through an additional PI controller to achieve power distribution between DC ports. The power distribution method based on this strategy requires the design of a complex space vector modulation algorithm, and the control effect is not ideal, resulting in large DC port power ripple. Therefore, it is urgent to develop a power distribution method for a single-stage multi-port photovoltaic storage system that does not require a complex modulation algorithm, and ensures an ideal control effect and avoids the generation of large DC port power ripple. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a single-stage multi-port optical storage system power distribution method with ripple suppression function, which 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 realizing 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 in that it includes 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 components v mentioned above into the original three-phase modulated signal, which respectively play the role of regulating power distribution and suppressing DC port power ripple. zs1 and zero sequence component v zs2 , and obtain the final three-phase modulation signal;

[0010] (4) Compare the 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;

[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 grid-side voltage regulation of the single-stage multi-port photovoltaic storage system.

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

[0013] 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.

[0014] At the same time, the single-stage multi-port optical storage system power allocation 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 only through a simple carrier modulation algorithm, and effectively suppress the generation of power ripple at the DC port. It solves the technical problem that the traditional power distribution method relies on a complex space vector modulation algorithm and the power ripple at the DC port 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 It is a flow chart of a power allocation method for a single-stage multi-port optical storage system with ripple suppression function of the present invention;

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

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

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

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

[0022] The specific implementation of the present invention is described below 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 the detailed description of known functions and designs may dilute the main content of the present invention, these 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 one of the three phases a, b, and c. In terms of topological characteristics, it has one AC output port and two DC output ports, and the DC port connected to photovoltaic is called the upper port, and the DC port connected to energy storage is called the lower port.

[0025] Combine the following Figure 2, the power allocation 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 the energy storage device through the power management module of the photovoltaic power generation system, and give the upper port reference power P 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 port and the lower port respectively;

[0031] S1.3: According to 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 previous power frequency cycle 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 previous power frequency cycle T k-1 The historical port power P at the same sampling time h,k-1 Compared with the 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 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 , 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 by adopting an iterative learning strategy. k The zero-sequence component can avoid the unsatisfactory power distribution effect caused by the switching control characteristics, which will bring about a large DC port power ripple.

[0046] S3: Inject the zero-sequence components v mentioned above into the original three-phase modulated signal, which respectively play the role of regulating power distribution and suppressing DC port power ripple. zs1,k and zero sequence component v zs2,k , and obtain the final three-phase modulated signal.

[0047] S3.1: Superposition of the zero-sequence components v above, which respectively play the role of regulating power distribution and suppressing 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: The zero-sequence component to be injected is limited to prevent it from causing the three-phase modulation signal to exceed the modulation range, and the constraint relationship is as follows:

[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 modulation signal, the established power distribution target is achieved and the power ripple generation of the DC port is effectively suppressed without affecting the regulation of the grid side voltage.

[0055] S4: Compare the obtained final three-phase modulation 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 with inconsistent amplitudes of the upper and lower carrier waves is generated, where both the upper and lower carrier waves are 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 / 2 range.

[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 switch tubes on the three-phase bridge arms in the single-stage multi-port photovoltaic storage system, so as to adjust the grid-side voltage of the single-stage multi-port photovoltaic 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] Finally, the power distribution between DC ports is performed based on carrier modulation, which avoids the complex design of space vector modulation algorithm. At the same time, the zero-sequence component of the power distribution is compensated by iterative learning strategy, which can effectively suppress the power ripple of DC port.

[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 of the grid side is P gref =1000W.

[0064] like Figure 3 As shown, the steady-state performance of the photovoltaic power generation system under 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 of the single-stage multi-port photovoltaic storage system and its total harmonic distortion index THD, it can be seen that under the power allocation method proposed in this embodiment, the photovoltaic storage power generation system can stably operate under unbalanced port voltage conditions, and its operating state is not affected by changes in the port voltage.

[0065] like Figure 4 As shown in the figure, the working conditions of the photovoltaic power generation system under three different port power allocation conditions are observed. Among them, under the rated power condition on 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. By observing the operating status of the single-stage multi-port photovoltaic storage system and the output power of the DC port, it can be seen that the output power of the upper port can be adjusted according to the given port power reference value, and the voltage and current on the grid side can still be stably maintained in a sinusoidal state, indicating that the method proposed in the present invention successfully realizes the power allocation of the single-stage multi-port photovoltaic 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 scheme proposed in this embodiment has a smaller port power ripple than the traditional scheme, which means 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 those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A single-stage multi-port optical storage system power allocation 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; (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 ; (3) Inject the zero-sequence components v mentioned above into the original three-phase modulated signal, which respectively play the role of regulating power distribution and suppressing DC port power ripple. zs1 and zero sequence component v zs2 , and obtain the final three-phase modulation signal; (4) Compare the 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; (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 grid-side voltage regulation of the single-stage multi-port photovoltaic storage system.

2. The single-stage multi-port optical storage system power allocation method with ripple suppression function according to claim 1, characterized in that: The zero sequence component v zs1,k The specific generation process is: (2.1) 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 ; (2.2) 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 port and the lower port respectively; (2.3), 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 (2.4), 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 Wherein, k1 represents the feedback adjustment coefficient.

3. The single-stage multi-port optical storage system power allocation method with ripple suppression function according to claim 1, characterized in that: The zero sequence component v zs2,k The specific generation process is: (3.1) 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 (3.2), 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 (3.3) 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 iterative learning strategy adjustment coefficient.

4. The single-stage multi-port optical storage system power allocation 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: (4.1), 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 (4.2), for the zero-sequence component v zs,k The limiting process is performed 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; (4.3) The zero-sequence component after limiting Injected into the original three-phase modulated signal to obtain the final three-phase modulated signal 5. The single-stage multi-port optical storage system power allocation method with ripple suppression function according to claim 1, characterized in that: The method for generating the digital switch signal is: (5.1) Based on the current port voltage, an asymmetric carrier wave with inconsistent amplitudes of the upper carrier wave and the lower carrier wave is generated, where both the upper and lower carrier waves are triangular waves with the same phase and frequency. l -V h / 2~V h / 2 range, the download wave is -V h / 2~V l -V h / 2 range changes; (5.2) and finally obtain the 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.

6. The single-stage multi-port optical storage system power allocation method with ripple suppression function according to claim 1, characterized in that: The action 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 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.

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