Photovoltaic power station Boost converter and inverter coordination control method based on sliding mode algorithm

Abstract

The invention relates to the technical field of power system control, in particular to a photovoltaic power station Boost converter and inverter coordination control method based on a sliding mode algorithm, and the method comprises the steps: building a photovoltaic array model, a Boost converter model and an inverter model; the output voltage and the output current of the photovoltaic array are sampled, through maximum power point control based on a sliding mode algorithm, the photovoltaic array can continuously output the maximum power, and the utilization efficiency of solar energy is improved; the Boost converter is coupled with the inverter by using the relation between the DC side bus voltage of the inverter and the output active power of the inverter; and controlling the DC bus voltage and the output active power of the photovoltaic power station to be set stable values in combination with inverter constant power control. According to the method, the oscillation problem existing in a traditional coordination control strategy can be relieved, the robustness and the anti-interference capability of the photovoltaic power station are improved, the overall performance of the photovoltaic power station is improved, and application of renewable energy sources is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of power system control, and in particular to a method for coordinated control of a Boost converter and an inverter of a photovoltaic power station based on a sliding mode algorithm. Background Art

[0002] With the continuous growth of the world economy and the steady increase in population, global energy demand continues to rise, bringing serious environmental pollution and climate change problems. In order to cope with these problems, photovoltaic energy, as a clean and renewable energy, has received widespread attention.

[0003] As an important means to achieve low-carbon transformation, photovoltaic power stations need to continuously optimize their coordinated control strategies to improve power generation efficiency, stabilize grid operation, reduce costs, and effectively integrate photovoltaic energy into the power system. However, the existing traditional coordinated control methods of photovoltaic power stations have oscillation problems, which affect the stable operation of the grid. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and propose a coordinated control method of the boost converter and inverter of a photovoltaic power station based on a sliding mode algorithm, which can alleviate the oscillation problem existing in the traditional control method and improve the robustness and anti-interference ability of the photovoltaic power station itself.

[0005] To achieve the above object, the present invention adopts the following specific technical solutions:

[0006] The present invention provides a photovoltaic power station boost converter and inverter coordinated control method based on a sliding mode algorithm, comprising the following steps:

[0007] S1. Establish a photovoltaic array model, a Boost converter model and an inverter model, and design circuit parameters for the Boost converter model;

[0008] S2, sampling the output voltage and output current of the photovoltaic array, and through the maximum power point control based on the sliding mode algorithm, the photovoltaic array can continuously output the maximum power, thereby improving the utilization efficiency of solar energy;

[0009] S3, using the relationship between the DC side bus voltage of the inverter and the output active power of the inverter, coupling the Boost converter with the inverter;

[0010] S4. Combined with the inverter constant power control, the DC bus voltage and output active power of the photovoltaic power station are controlled to the set stable values.

[0011] Furthermore, in step S1, the circuit parameters of the Boost converter model are designed as follows:

[0012] Input voltage V sWith output voltage V o The relationship is:

[0013]

[0014] Input current I s With the output current I o The relationship is:

[0015] I o =(1-D)·I s ;

[0016] The parameter design formula of the energy storage inductor L is:

[0017]

[0018] The parameters of the output filter capacitor C are designed as follows:

[0019]

[0020] Input filter capacitor C s The parameters are designed as:

[0021]

[0022] Where V s is the input voltage, V o is the output voltage, V L is the inductor voltage, I s is the input current, I o is the output current, D is the duty cycle, P i is the input power, P o is the output power, T s is the control signal period, η L is the output current ripple rate, η C is the output voltage ripple rate, η s is the input voltage ripple rate.

[0023] Further, in step S2, the maximum power point control based on the sliding mode algorithm is specifically as follows:

[0024]

[0025] Where D z is the duty cycle of the Boost converter switch, s is the sliding surface, and E is the approaching change limit; i pv is the PV array output current, u pv is the PV array output voltage.

[0026] Furthermore, in step S3, the relationship between the DC side bus voltage of the inverter and the output active power of the inverter is used to couple the Boost converter to the inverter as follows:

[0027] The active power output of the inverter is set to be affected only by the d-axis current i after the three-phase current is transformed by Park. d When the DC bus voltage is lower than the set reference value, the active power output of the inverter is reduced and the energy delivered to the grid is reduced to maintain balance and stability. At this time, the energy generated exceeds the transmission capacity of the inverter, the energy storage capacitor begins to charge, and the bus voltage gradually increases to the target level; if the bus voltage exceeds the reference value, the active power output of the inverter is increased to adjust the bus voltage back to the set normal range. The bus voltage u dc The change formula is:

[0028]

[0029] In the formula, C dc is the DC side capacitance, e d It is the d-axis voltage of the three-phase voltage of the power grid after Park transformation.

[0030] Furthermore, in step S4, in combination with the inverter constant power control, the DC bus voltage and output active power of the photovoltaic power station are controlled to be set stable values ​​as follows:

[0031]

[0032] Where V d It represents the d-axis voltage of the three-phase voltage on the inverter AC side after Park transformation, V q represents the q-axis voltage on the AC side of the inverter, e q represents the q-axis voltage on the grid side, ω represents the grid frequency, L0 represents the inductance of the inverter L-type filter, represents the d-axis current target value, Indicates the q-axis current target value, K p , K i represents the parameters of the PI controller, Indicates the DC bus voltage target value.

[0033] The present invention can achieve the following technical effects:

[0034] The present invention can alleviate the oscillation problem existing in traditional coordinated control strategies, improve the robustness and anti-interference ability of photovoltaic power stations themselves, help promote the development of photovoltaic technology, improve the overall performance of photovoltaic power stations, promote the popularization and application of renewable energy, and contribute to the construction of a green and low-carbon future energy system.

[0035] By constructing specific working conditions and verifying them on the simulation platform, it was found that the coordinated control strategy of the photovoltaic power station Boost converter and inverter based on the sliding mode algorithm can effectively maintain the stability of the DC voltage and output active power of the photovoltaic power station, and can improve the utilization efficiency of solar energy in the photovoltaic power station, which is helpful to promote the development of photovoltaic technology, improve the overall performance of photovoltaic power stations, and promote the popularization and application of renewable energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of a method for coordinated control of a Boost converter and an inverter of a photovoltaic power station based on a sliding mode algorithm provided in an embodiment of the present invention;

[0037] Figure 2 is a schematic structural diagram of a photovoltaic array model provided according to an embodiment of the present invention;

[0038] Figure 3 is a structural schematic diagram of a Boost converter model provided according to an embodiment of the present invention;

[0039] Figure 4 is a structural schematic diagram of an inverter model provided according to an embodiment of the present invention;

[0040] Figure 5 is a set working status data diagram provided according to an embodiment of the present invention;

[0041] Figure 6 is a waveform diagram of active and reactive power outputted by the inverter side according to an embodiment of the present invention;

[0042] Figure 7 is a BOOST converter output voltage waveform diagram provided according to an embodiment of the present invention;

[0043] Figure 8 is a waveform diagram of output current and output voltage of a photovoltaic cell provided in an embodiment of the present invention;

[0044] Fig. 9 4 is a photovoltaic cell output power waveform diagram provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0046] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0047] The embodiment of the present invention provides a photovoltaic power station boost converter and inverter coordinated control method based on sliding mode algorithm, the process is as follows Figure 1 As shown, the following steps are included:

[0048] S1. Establish a photovoltaic array model, a Boost converter model and an inverter model, and design circuit parameters for the Boost converter model.

[0049] The structures of the photovoltaic array model, Boost converter model and inverter model are as follows: Figure 2 , Figure 3 as well as Figure 4 As shown, the circuit parameter design of the Boost converter model is as follows:

[0050] Input voltage V s With output voltage V o The relationship is:

[0051]

[0052] Input current L s With the output current I o The relationship is:

[0053] I o =(1-D)·I s ; (2)

[0054] The parameter design formula of the energy storage inductor L is:

[0055]

[0056] The parameters of the output filter capacitor C are designed as follows:

[0057]

[0058] Input filter capacitor C s The parameters are designed as:

[0059]

[0060] Where V s is the input voltage, V o is the output voltage, V L is the inductor voltage, I s is the input current, I o is the output current, D is the duty cycle, P i is the input power, P o is the output power, T s is the control signal period, η L is the output current ripple rate, ηC is the output voltage ripple rate, η s is the input voltage ripple rate.

[0061] S2, sampling the output voltage and output current of the photovoltaic array, and through the maximum power point control based on the sliding mode algorithm, the photovoltaic array can continuously output the maximum power and improve the utilization efficiency of solar energy.

[0062] The maximum power point control based on the sliding mode algorithm is as follows:

[0063]

[0064] Where D z is the duty cycle of the Boost converter switch, s is the sliding surface, and E is the approaching change limit; i pv is the PV array output current, u pv is the PV array output voltage.

[0065] The control signal output by the controller is the duty cycle of the switching device in the Boost converter. By changing the duty cycle of the switching device, the working condition of the external circuit is changed, so that the photovoltaic array outputs maximum power.

[0066] S3. The Boost converter is coupled to the inverter by utilizing the relationship between the DC side bus voltage of the inverter and the output active power of the inverter.

[0067] The active power output of the inverter is set to be affected only by the d-axis current i after the three-phase current is transformed by Park. d When the DC bus voltage is lower than the set reference value, in order to maintain the balance and stability of the system, the active power output of the inverter is reduced to reduce the energy delivered by the system to the grid. At this time, the energy generated by the photovoltaic system or battery energy storage system exceeds the current transmission capacity of the inverter, and the energy storage capacitor inside the system begins to charge, and the bus voltage is gradually increased to the target level. If the bus voltage exceeds the reference value, the bus voltage will be adjusted back to the set normal range by increasing the active power output of the inverter.

[0068] Bus voltage u dc The change formula is:

[0069]

[0070] In the formula, C dc is the DC side capacitance, e d It is the d-axis voltage of the three-phase voltage of the power grid after Park transformation.

[0071] S4: Based on the coupling of S3, combined with the inverter constant power control, the DC bus voltage and output active power of the photovoltaic power station are controlled to the set stable values.

[0072]

[0073] Where V d Represents the d-axis voltage of the three-phase voltage on the inverter AC side after Park transformation, V q represents the q-axis voltage on the AC side of the inverter, e q represents the q-axis voltage on the grid side, ω represents the grid frequency, L0 represents the inductance of the inverter L-type filter, represents the d-axis current target value, Represents the q-axis current target value, K p , K i represents the parameters of the PI controller, Represents the target value of DC bus voltage.

[0074] Construct specific working conditions and verify them on the simulation platform. The working conditions set are as follows: Figure 5 The simulation results are shown in Figure 6 to Figure 9 As shown, Figure 6 It is the waveform diagram of active and reactive power output on the inverter side. Figure 7 This is the output voltage waveform of the BOOST converter. Figure 8 This is the output current and voltage waveform of the photovoltaic cell. Fig. 9 The output power waveform of the photovoltaic cell is shown in Figure 2. According to the simulation results, the coordinated control strategy of the photovoltaic power station Boost converter and inverter based on the sliding mode algorithm can effectively maintain the stability of the DC voltage and output active power of the photovoltaic power station, and can improve the utilization efficiency of solar energy in the photovoltaic power station, which is helpful to promote the development of photovoltaic technology, improve the overall performance of photovoltaic power stations, and promote the popularization and application of renewable energy.

[0075] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0076] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

[0077] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A photovoltaic power station boost converter and inverter coordinated control method based on sliding mode algorithm, characterized in that: The steps include: S1. Establishing a photovoltaic array model, a Boost converter model and an inverter model, and designing circuit parameters for the Boost converter model; S2, sampling the output voltage and output current of the photovoltaic array, and through the maximum power point control based on the sliding mode algorithm, the photovoltaic array can continuously output the maximum power, thereby improving the utilization efficiency of solar energy; S3, using the relationship between the DC side bus voltage of the inverter and the output active power of the inverter, coupling the Boost converter with the inverter; S4. Combined with the inverter constant power control, the DC bus voltage and output active power of the photovoltaic power station are controlled to the set stable values.

2. The photovoltaic power station boost converter and inverter coordinated control method based on sliding mode algorithm according to claim 1 is characterized in that: In step S1, the Boost converter model circuit parameters are designed as follows: Input voltage V s With output voltage V o The relationship is: Input current I s With the output current I o The relationship is: I o =(1-D)·I s ; The parameter design formula of the energy storage inductor L is: The parameters of the output filter capacitor C are designed as follows: Input filter capacitor C s The parameters are designed as: Where V s is the input voltage, V o is the output voltage, V L is the inductor voltage, I s is the input current, I o is the output current, D is the duty cycle, P i is the input power, P o is the output power, T s is the control signal period, η L is the output current ripple rate, η C is the output voltage ripple rate, η s is the input voltage ripple rate.

3. The photovoltaic power station boost converter and inverter coordinated control method based on sliding mode algorithm according to claim 1 is characterized in that: In step S2, the maximum power point control based on the sliding mode algorithm is specifically as follows: Where D z is the duty cycle of the Boost converter switch, s is the sliding surface, and E is the approaching change limit; i pv is the PV array output current, u pv is the PV array output voltage.

4. The photovoltaic power station boost converter and inverter coordinated control method based on sliding mode algorithm according to claim 1 is characterized in that: In step S3, the relationship between the DC bus voltage of the inverter and the active power output of the inverter is used to couple the Boost converter to the inverter as follows: The active power output of the inverter is set to be affected only by the d-axis current i after the three-phase current is transformed by Park. d When the DC bus voltage is lower than the set reference value, the active power output of the inverter is reduced and the energy delivered to the grid is reduced to maintain balance and stability. At this time, the energy generated exceeds the transmission capacity of the inverter, the energy storage capacitor begins to charge, and the bus voltage gradually increases to the target level; if the bus voltage exceeds the reference value, the active power output of the inverter is increased to adjust the bus voltage back to the set normal range. The bus voltage u dc The change formula is: In the formula, C dc is the DC side capacitance, e d It is the d-axis voltage of the three-phase voltage of the power grid after Park transformation.

5. The photovoltaic power station boost converter and inverter coordinated control method based on sliding mode algorithm according to claim 1 is characterized in that: In step S4, in combination with the inverter constant power control, the DC bus voltage and output active power of the photovoltaic power station are controlled to set stable values ​​as follows: Where V d It represents the d-axis voltage of the three-phase voltage on the inverter AC side after Park transformation, V q represents the q-axis voltage on the AC side of the inverter, e q represents the q-axis voltage on the grid side, ω represents the grid frequency, L0 represents the inductance of the inverter L-type filter, represents the d-axis current target value, Indicates the q-axis current target value, K p , K i represents the parameters of the PI controller, Indicates the target value of DC bus voltage.

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