A network coordination control method and device

Abstract

The present application discloses a method and device for coordinated control of a network, which relates to the field of power control technology. The main purpose is to improve the reliability of a two-stage current source inverter, thereby ensuring the stable operation of a network-type weak power grid. The main technical solution of the present application is: obtaining the active power error of the second-stage current source inverter and the freewheeling inductor current error of the first-stage step-down DC converter; processing the active power error using a proportional controller in a parallel framework, and processing the freewheeling inductor current error using a proportional integral controller to obtain the three-phase voltage phase of a common coupling point. The parallel framework is used to characterize the framework mode for synchronous processing of the active power error and the freewheeling inductor current error; based on the three-phase voltage phase and voltage drop compensation strategy, the two-stage current source inverter is coordinated and controlled to ensure the stable operation of the network-type weak power grid. The present application is used for coordinated control of a network.

Description

Technical Field

[0001] The present application relates to the field of power control technology, and in particular to a network coordination control method and device. Background Art

[0002] The two-stage current source inverter is a topological structure with important advantages for photovoltaic grid-connected systems in microgrids. It is widely used in weak grids with large grid impedance. The topological structure of the cascaded step-down DC converter and the current source inverter can generate an AC voltage with a wider range of amplitudes at the common coupling point, and it can achieve good and stable grid-connected operation in actual situations where the DC side input voltage is too low or too high. Therefore, it is necessary to calculate the three-phase voltage phase at the common coupling point to coordinate the control of the two-stage current source inverter based on the three-phase voltage phase.

[0003] Currently, existing literature generally controls the first and second stages of a two-stage current source inverter separately. However, due to the power imbalance problem in the two-stage current source inverter, relying on only a single stage in the converter to calculate the three-phase voltage phase inevitably leads to slow calculation speed. In addition, the use of the zero vector results in large losses in the two-stage current source inverter, affecting the reliability of the two-stage current source inverter and making it impossible to ensure the stable operation of the grid-type weak power grid. Therefore, to solve the above problems, a grid-type coordinated control method is urgently needed. Summary of the Invention

[0004] In view of the above problems, the present application provides a network coordination control method and device, the main purpose of which is to improve the reliability of the two-stage current source inverter, thereby ensuring the stable operation of the network-type weak power grid.

[0005] To solve the above technical problems, this application proposes the following solutions:

[0006] In a first aspect, the present application provides a network coordination control method, which is applied to a network-type weak power grid deploying a two-stage current source inverter, wherein the two-stage current source inverter is composed of a first-stage step-down DC converter and a second-stage current source inverter cascaded, and the method includes:

[0007] Obtaining an active power error of the second-stage current source inverter and a freewheeling inductor current error of the first-stage step-down DC converter;

[0008] In a parallel framework, a proportional controller is used to process the active power error, and a proportional-integral controller is used to process the freewheeling inductor current error to obtain a three-phase voltage phase at a common coupling point. The parallel framework is used to represent a framework mode for synchronously processing the active power error and the freewheeling inductor current error.

[0009] The two-stage current source inverter is coordinated and controlled based on the three-phase voltage phase and voltage drop compensation strategy to ensure stable operation of the grid-type weak power grid.

[0010] In a second aspect, the present application provides a network coordination control device for a network-forming weak power grid deployed with a two-stage current source inverter, wherein the two-stage current source inverter is composed of a first-stage step-down DC converter and a second-stage current source inverter cascaded, and the device includes:

[0011] an acquiring unit, configured to acquire an active power error of the second-stage current source inverter and a freewheeling inductor current error of the first-stage step-down DC converter;

[0012] a processing unit, configured to process the active power error of the acquisition unit using a proportional controller and the freewheeling inductor current error of the acquisition unit using a proportional-integral controller in a parallel framework to obtain a three-phase voltage phase at a common coupling point, wherein the parallel framework is configured to represent a framework mode for synchronously processing the active power error and the freewheeling inductor current error;

[0013] A control unit is used to coordinately control the two-stage current source inverter based on the three-phase voltage phase and voltage drop compensation strategy of the processing unit to ensure stable operation of the grid-type weak power grid.

[0014] In order to achieve the above-mentioned purpose, according to the third aspect of the present application, a storage medium is provided, which includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the network coordination control method of the above-mentioned first aspect.

[0015] In order to achieve the above-mentioned purpose, according to a fourth aspect of the present application, a processor is provided, which is used to run a program, wherein the program executes the networking coordination control method of the above-mentioned first aspect when running.

[0016] By means of the above technical solution, the present application provides a method and device for coordinated control of a network, which, when coordinated control of a network is required, first obtains the active power error of the second-stage current source inverter and the freewheeling inductor current error of the first-stage step-down DC converter, and then uses a proportional controller to process the active power error and a proportional-integral controller to process the freewheeling inductor current error in a parallel framework to obtain the three-phase voltage phase of the common coupling point. The parallel framework is used to characterize the framework mode for synchronous processing of the active power error and the freewheeling inductor current error. Finally, the two-stage current source inverter is coordinated and controlled based on the three-phase voltage phase and voltage drop compensation strategy to ensure stable operation of the network-type weak power grid. Through the technical solution provided in this application, the active power error of the second-stage current source inverter and the freewheeling inductor current error of the first-stage step-down DC converter can be coordinated and synchronously processed, that is, the three-phase voltage phase of the common coupling point is calculated by combining two single stages, thereby improving the calculation speed of the three-phase voltage phase, thereby accelerating the construction of the three-phase voltage at the common coupling point, so that the two-stage current source inverter can be quickly and stably connected to the grid, and the voltage drop compensation strategy is used to compensate for the loss of the two-stage current source inverter, eliminating the use of zero vector, reducing the loss of the two-stage current source inverter, improving the reliability of the two-stage current source inverter, and ensuring the stable operation of the grid-type weak power grid.

[0017] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0019] Figure 1 A flowchart of a network coordination control method provided by an embodiment of the present application is shown;

[0020] Figure 2 A flowchart of another network coordination control method provided in an embodiment of the present application is shown;

[0021] Figure 3 A block diagram showing the composition of a network coordination control device provided in an embodiment of the present application is shown;

[0022] Figure 4 A block diagram showing the composition of another network coordination control device provided in an embodiment of the present application is shown;

[0023] Figure 5 To illustrate the specific topology structure of the two-stage current source inverter provided in the embodiment of the present application;

[0024] Figure 6 A control schematic diagram of calculating the three-phase voltage phase at a common coupling point based on a parallel framework provided by an embodiment of the present application is shown;

[0025] Figure 7 A schematic diagram showing the control of generating a wave function and a reference modulation wave provided by an embodiment of the present application is shown;

[0026] Figure 8 2 is a control diagram illustrating generation of a reference duty cycle corresponding to a first-stage step-down DC converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0027] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0028] Currently, existing literature generally controls the first and second stages of a two-stage current source inverter separately. However, due to the power imbalance problem in the two-stage current source inverter, if only relying on a single stage in the converter to calculate the three-phase voltage phase will inevitably lead to slow calculation speed. In addition, due to the use of zero vector, the loss of the two-stage current source inverter is large, affecting the reliability of the two-stage current source inverter and unable to guarantee the stable operation of the grid-type weak power grid.

[0029] After research, the inventors found that the first and second stages of the two-stage current source inverter can be combined with collaborative control to realize the calculation of the three-phase voltage phase of the common coupling point, and a voltage drop compensation strategy can be set to compensate for the loss of the two-stage current source inverter, thereby eliminating the use of zero vector, improving the reliability of the two-stage current source inverter, and ensuring the stable operation of the grid-type weak power grid.

[0030] Based on the above considerations, the embodiment of the present application provides a network coordination control method, which can improve the reliability of the two-stage current source inverter and thus ensure the stable operation of the network type weak power grid. The specific execution steps are as follows: Figure 1 As shown in FIG, a grid-type weak power grid is applied to deploy a two-stage current source inverter. The two-stage current source inverter is composed of a first-stage step-down DC converter and a second-stage current source inverter in cascade, including:

[0031] 101. Obtain the active power error of the second-stage current source inverter and the freewheeling inductor current error of the first-stage step-down DC converter.

[0032] In this embodiment, it should be noted that the two-stage current source inverter is composed of a first-stage step-down DC converter and a second-stage current source inverter in cascade. Figure 5 As shown, it includes the first-stage Buck step-down DC converter (first-stage Buck DC converter) part, the second-stage current source inverter part, the freewheeling inductor part L1, L2, and the DC link capacitor part C link1 、C link2 . Among them, the main function of the first-stage step-down DC converter is to step down the input high-voltage DC power to a lower voltage suitable for subsequent circuit processing. This converter usually adopts switching power supply technology to control the on and off of the switch tube to step down the input voltage to the required output voltage. This step-down converter can provide a stable output voltage and has good regulation performance when the load changes. The function of the second-stage current source inverter is to convert DC power into AC power to supply the load. This inverter adopts a current source topology, which can provide a stable output current and has good dynamic response performance when the load changes. The current source inverter can achieve precise control of the load by controlling the magnitude and phase of the output current, and is suitable for various loads that require AC power. In this step, the active power error of the second-stage current source inverter can be obtained based on the difference between the active power reference value and the active power sampling value of the second-stage current source inverter, and the freewheeling inductor current error of the first-stage step-down DC converter can be obtained based on the difference between the freewheeling inductor current reference value and the freewheeling inductor current sampling value of the first-stage step-down DC converter, so as to execute the subsequent step 102.

[0033] 102. In the parallel framework, the active power error is processed using a proportional controller, and the freewheeling inductor current error is processed using a proportional integral controller to obtain the three-phase voltage phase of the common coupling point. In this step, the main functions of the proportional controller (P controller) and the proportional controller (PI controller) are to eliminate the active power error and the freewheeling inductor current error, that is, to convert these two error signals into corresponding control signals to adjust the output of the first-stage buck DC converter and the second-stage current source inverter to make the two-stage current source inverter system more stable. Among them, the parallel framework is used to characterize the framework mode for synchronous processing of the active power error and the freewheeling inductor current error. That is, the active power error and the freewheeling inductor current error are processed synchronously, so that the three-phase voltage phase of the common coupling point is calculated collaboratively based on the second-stage current source inverter and the first-stage buck DC converter, thereby improving the calculation speed of the three-phase voltage phase, thereby accelerating the construction of the three-phase voltage at the common coupling point, and making the two-stage current source inverter quickly and stably connected to the grid. The specific execution process can be referred to. Figure 6 , and the formula is as follows:

[0034]

[0035] Among them, P g_ref is the active power reference value of the second-stage current source inverter, P g is the active power sampling value of the second-stage current source inverter, I L2_ref is the reference value of the freewheeling inductor current of the first-stage step-down DC converter, I L2 is the freewheeling inductor current sampling value of the first-stage buck DC converter. In practical applications, both the active power sampling value of the second-stage current source inverter and the freewheeling inductor current sampling value of the first-stage buck DC converter need to be respectively added with a low-pass filter. Therefore, and It is used to filter out high-frequency harmonics to avoid large high-frequency fluctuations in the three-phase voltage phase of the calculated common coupling point, which ultimately affects the quality of the grid-connected current.

[0036] 103. Based on the three-phase voltage phase and voltage drop compensation strategy, the two-stage current source inverter is coordinated and controlled to ensure the stable operation of the grid-type weak power grid.

[0037] In this step, the voltage drop compensation strategy is used to characterize the strategy for compensating for the voltage losses corresponding to the active devices and passive devices in the first-stage step-down DC converter in the two-stage current source inverter. The DC link capacitor current in the second-stage current source inverter can be controlled so that its error is corrected to 0, thereby compensating for the voltage drop loss. Alternatively, a measured voltage drop loss can be set and compensation can be performed based on it. This embodiment does not limit this. If the DC link capacitor current is controlled, the DC link capacitor current error is processed using a proportional-integral controller to obtain a corresponding high-frequency voltage control component. It should be noted that the DC link capacitor current reference value is 0 at this time. In addition, a three-phase current reference value of a common coupling point is determined, and a fluctuation function of the first-stage step-down DC conversion period is determined by the three-phase current reference value and the three-phase voltage phase. The average value of the bridge arm input voltage is obtained by using the fluctuation function and the three-phase voltage amplitude reference value of the common coupling point, so as to obtain a reference duty cycle corresponding to the first-stage step-down DC converter based on the high-frequency voltage control component, the average value of the bridge arm input voltage and the bridge arm input voltage sampling value. The two-stage current source inverter is coordinated and controlled based on the reference duty cycle, so as to achieve the same regular fluctuation of the freewheeling inductor in the second-stage current source inverter and the freewheeling inductor in the first-stage step-down DC converter, and then all zero vectors in the two-stage current source inverter are eliminated under the premise of maintaining a high grid-connected current quality, thereby greatly reducing the number of switches, reducing system losses, improving the reliability of the two-stage current source inverter, and ensuring the stable operation of the grid-type weak power grid.

[0038] Based on the above Figure 1It can be seen from the implementation method that, by means of the above technical scheme, a grid coordination control method provided by the present application is to first obtain the active power error of the second-stage current source inverter and the freewheeling inductor current error of the first-stage step-down DC converter when grid coordination control is required, and then use the proportional controller to process the active power error in the parallel framework, and use the proportional integral controller to process the freewheeling inductor current error to obtain the three-phase voltage phase of the common coupling point. The parallel framework is used to characterize the framework mode for synchronous processing of the active power error and the freewheeling inductor current error. Finally, the two-stage current source inverter is coordinated and controlled based on the three-phase voltage phase and voltage drop compensation strategy to ensure stable operation of the grid-type weak power grid. Through the technical solution provided in this application, the active power error of the second-stage current source inverter and the freewheeling inductor current error of the first-stage step-down DC converter can be coordinated and synchronously processed, that is, the three-phase voltage phase of the common coupling point is calculated by combining two single stages, thereby improving the calculation speed of the three-phase voltage phase, thereby accelerating the construction of the three-phase voltage at the common coupling point, so that the two-stage current source inverter can be quickly and stably connected to the grid, and the voltage drop compensation strategy is used to compensate for the loss of the two-stage current source inverter, eliminating the use of zero vector, reducing the loss of the two-stage current source inverter, improving the reliability of the two-stage current source inverter, and ensuring the stable operation of the grid-type weak power grid.

[0039] Furthermore, the preferred embodiment of the present application is in the above Figure 1 Based on this, a detailed description of the process of network coordination control is given, and the specific steps are as follows: Figure 2 Shown, including:

[0040] 201. Obtain the active power error of the second-stage current source inverter and the freewheeling inductor current error of the first-stage step-down DC converter.

[0041] This step is combined with the description of step 101 in the above method, and the same content will not be repeated here.

[0042] 202. In a parallel framework, a proportional controller is used to process the active power error, and a proportional-integral controller is used to process the freewheeling inductor current error to obtain the three-phase voltage phase at the common coupling point.

[0043] This step is combined with the description of step 102 in the above method, and the same contents will not be repeated here.

[0044] 203. Determine a three-phase current reference value of a common coupling point based on the active power error and reactive power error of the second-stage current source inverter, and determine a freewheeling inductor current reference value of the first-stage step-down DC converter based on the three-phase current reference value of the common coupling point.

[0045] In this step, the three-phase current reference value of the common coupling point can be determined based on the active power error and reactive power error of the second-stage current source inverter. Specifically, the active power error and reactive power error are processed by a proportional-integral controller to obtain a three-phase voltage d-axis DC component reference value and a three-phase voltage q-axis DC component reference value at the common coupling point; based on the three-phase voltage d-axis DC component reference value and the three-phase voltage d-axis DC component sampled value at the common coupling point, as well as the three-phase voltage q-axis DC component reference value and the three-phase voltage q-axis DC component sampled value at the common coupling point, the three-phase voltage d-axis DC component error and the three-phase voltage q-axis DC component error at the common coupling point are obtained; the three-phase voltage q-axis DC component error and the three-phase voltage d-axis DC component error are processed by a proportional-integral controller to obtain a three-phase current reference value at the common coupling point; and the unidirectional current reference value with the largest absolute value among the three-phase current reference values ​​is used as the freewheeling inductor current reference value of the first-stage step-down DC converter.

[0046] Among them, the active power reference value P of the second-level current source inverter is q_ref and reactive power reference value Q q_ref The calculation formula is as follows:

[0047] P g_ref =I a_ref ·V a_ref +I b_ref ·V b_ref +I c_ref ·V c_ref

[0048]

[0049] It should be noted that the three-phase voltage d-axis DC component reference value and q-axis DC component reference value refer to two components in the dq coordinate system, which is used to describe three-phase alternating current, where the d-axis represents the active component and the q-axis represents the reactive component. For a two-stage current source inverter, the purpose of controlling the d-axis component and the q-axis component is to achieve decoupling control of active power and reactive power, thereby improving system performance and stability. Among them, the three-phase current can be referred to Figure 5 Indicated as I a , I b_ , I c , and the three-phase voltage d-axis DC component reference value and q-axis DC component reference value can be expressed as V d_ref and V q_ref The d-axis DC component sampling value and the q-axis DC component sampling value of the three-phase voltage can be expressed as V d_ and V qTherefore, the three-phase voltage d-axis DC component error and the three-phase voltage q-axis DC component error can be obtained by taking the difference between the two, and the proportional integral controller is used to process the two separately to obtain the three-phase current reference value, which can be referred to Figure 5 Indicated as I a_ref , I b_ref , I c_ref Accordingly, after obtaining the three-phase current reference values, the unidirectional current reference value with the largest absolute value can be selected as the freewheeling inductor current reference value of the first-stage step-down DC converter, so as to execute the subsequent step 204 .

[0050] 204. Determine a reference value of a d-axis DC component of the three-phase current at a common coupling point using the three-phase current reference value and the three-phase voltage phase.

[0051] In this step, the three-phase current d-axis DC component reference value at the common coupling point can be obtained using the three-phase current reference value and the three-phase voltage phase. The specific formula is as follows:

[0052] I d_ref =I a_ref ·cosθ+I b_ref ·cosθ+I c_ref cosθ

[0053] Among them, I d_ref is the reference value of the three-phase current d-axis DC component, and the three-phase current reference value is I a_ref , I b_ref , I c_ref , θ is the three-phase voltage phase.

[0054] 205. Determine a ripple function corresponding to the first-stage step-down DC converter according to a three-phase current d-axis DC component reference value and a freewheeling inductor current reference value.

[0055] In this step, a fluctuation function is used to characterize the fluctuation pattern of the output voltage of the first-stage step-down DC converter. By using the fluctuation function, the system can better control the converter output to adapt to changes in the load and ensure system stability. The fluctuation function can be determined by the three-phase current d-axis DC component reference value and the freewheeling inductor current reference value. Since there are three three-phase current reference values, in order to ensure that the freewheeling inductor current of the first-stage step-down DC converter can effectively provide the current required by the load, the unidirectional current reference value with the largest absolute value is selected to ensure that the current provided to the load is the largest to meet its needs. That is, the freewheeling inductor current reference value I of the first-stage step-down DC converter is obtained by taking the maximum absolute value. L2_ref =Max(Abs(I a_ref ,I b_ref ,I c_ref )), through I L2_refand I d_ref By dividing, we can calculate that different sectors have different wave functions. The specific formula is as follows:

[0056]

[0057] Among them, F(PCC) is the ripple function of the first-stage step-down DC converter, I d_ref is the reference value of the three-phase current d-axis DC component, and the three-phase current reference value is I L2_ref is the reference value of the freewheeling inductor current of the first-stage step-down DC converter, and θ is the phase of the three-phase voltage at the common coupling point.

[0058] Furthermore, in order to accurately control the pulse through the modulation wave, the specific execution process is: using the three-phase current reference value and the three-phase voltage phase to determine the three-phase current q-axis DC component at the common coupling point; based on the three-phase current d-axis DC component reference value of the common coupling point and the three-phase current d-axis DC component sampling value of the common coupling point, as well as the three-phase current q-axis DC component reference value of the common coupling point and the three-phase current q-axis DC component sampling value of the common coupling point, the three-phase current d-axis DC component error of the common coupling point and the three-phase current q-axis DC component error of the common coupling point are obtained; using the proportional-integral controller to process the three-phase current d-axis DC component error and the three-phase current q-axis DC component error respectively, to obtain the three-phase current d-axis reference modulation wave and the three-phase current q-axis reference modulation wave to perform pulse control on the second-stage current source inverter.

[0059] It should be noted that, in the stable state of the system (I q_ref =I q =0) is the q-axis DC component reference value of the three-phase current. Generally, the three-phase current reference value is converted into the dq coordinate system for easy control. The expression of the three-phase current reference value in the dq coordinate system is as follows:

[0060]

[0061] Among them, I d_ref is the reference value of the d-axis DC component of the three-phase current, I q_ref is the reference value of the q-axis DC component of the three-phase current, V d_ref is the reference value of the d-axis DC component of the three-phase current, V d_ is the sampling value of the d-axis DC component of the three-phase current, V q_ref is the reference value of the three-phase current Q-axis DC component, V q is the sampling value of the Q-axis DC component of the three-phase current.

[0062] The specific formula of the three-phase modulation wave in the dq coordinate system is as follows:

[0063]

[0064] Among them, T d_ref is the three-phase current d-axis reference modulation wave, T q_ref The three-phase current q-axis reference modulation wave can be adjusted to be a sine wave through the three-phase current d-axis reference modulation wave and the three-phase current q-axis reference modulation wave, thereby realizing pulse control of the second-stage current source inverter.

[0065] It should be noted that the specific algorithm logic of steps 203-205 can be referred to Figure 5 and Figure 7 .

[0066] 206. The average value of the bridge arm input voltage is obtained according to the fluctuation function and the three-phase voltage amplitude reference value of the common coupling point.

[0067] In this step, the three-phase voltage amplitude reference value at the common coupling point can be calculated based on the three-phase voltage d-axis DC component reference value at the common coupling point and the three-phase voltage q-axis DC component reference value at the common coupling point. The specific formula is as follows:

[0068]

[0069] Among them, V d_ref is the three-phase voltage d-axis DC component reference value and V q_ref The reference value of the q-axis DC component of the three-phase voltage is obtained by adding the squares of the two and then opening them to obtain the reference value of the three-phase voltage amplitude. However, since 1.5 times the grid voltage amplitude multiplied by the grid current amplitude equals the grid-connected power, 1.5 is a fixed coefficient in the instantaneous power calculation method. Therefore, when it is necessary to calculate the average value of the bridge arm input voltage, it is necessary to use the instantaneous power method to calculate the three-phase voltage amplitude reference value and the fluctuation function at the common coupling point to obtain the average value of the bridge arm input voltage. Substituting 1.5 into the formula, the specific formula is as follows: V m / F(PCC)=1.5V d_ref / F(6f)=V avg_pn , where V avg_pn The average bridge arm input voltage represents the coordinated control of the two-stage current source inverter in a parallel configuration based on the three-phase voltage phase and voltage drop compensation strategy. It is used to achieve the desired voltage amplitude and phase at the point of common coupling (PCC) to support stable grid operation. By adjusting the average bridge arm input voltage, the inverter output can be controlled to ensure system stability under load changes or other disturbances, facilitating execution of subsequent step 207.

[0070] 207. A proportional-integral controller is used to process the DC link capacitor current error in the second-stage current source inverter to obtain a high-frequency voltage control component.

[0071] Among them, the high-frequency voltage control component is used to characterize the voltage drop compensation corresponding to the first-stage step-down DC converter when the DC link capacitor current reference value is 0. Since each high-frequency action device and passive device in the first-stage step-down DC converter has different degrees of voltage drop due to its inherent parasitic parameters, that is, the theoretically calculated average value of the bridge arm input voltage will be different from the actual bridge arm input voltage sampling value. Therefore, it is necessary to control the DC link capacitor current in the second-stage current source inverter (the DC link capacitor current reference value I C1_ref =0) to introduce a high-frequency voltage control variable as the reference duty cycle of the first-stage step-down DC converter calculated by compensation voltage control theory. The specific formula is as follows:

[0072]

[0073] Among them, I C1_ref is the DC link capacitor current reference value, I C1 is the DC link capacitor current sampling value, which is processed by the proportional-integral controller to obtain a high-frequency voltage control variable so as to execute the subsequent step 208.

[0074] 208. Calculate the reference duty cycle corresponding to the first-stage step-down DC converter using the high-frequency voltage control component, the average value of the bridge arm input voltage, and the bridge arm input voltage sampling value, so as to coordinately control the two-stage current source inverter based on the reference duty cycle.

[0075] In this step, since the theoretically calculated average value of the bridge arm input voltage is different from the actual bridge arm input voltage sampling value, a high-frequency voltage control component is introduced to compensate for the reference duty cycle of the first-stage buck DC converter calculated by the voltage control theory. Based on this, the final expression of the first-stage buck DC converter is as follows:

[0076]

[0077] Among them, V avg_pn is the average value of the bridge arm input voltage, V dc is the bridge arm input voltage sampling value, is the high frequency voltage control component. For detailed algorithm logic, see Figure 7 Through the above control method, the freewheeling inductor current of the second-stage current source inverter can also follow the fluctuation function corresponding to the first-stage buck DC converter, that is, it fluctuates in the same law as the first-stage buck DC converter. The specific expression is as follows:

[0078] I L1_ref =I L2_ref =I d_ref ·F(PCC)

[0079] Among them, corresponding Figure 5 It can be seen that I L1_ref is the reference value of the freewheeling inductor current of the second-stage current source inverter, I L2_ref It is the reference value of the freewheeling inductor current of the first-stage step-down DC converter.

[0080] It should be noted that the specific algorithm logic of steps 206-208 can be referred to Figure 5 and Figure 8 .

[0081] Furthermore, as a response to the above Figure 1-2 The embodiment of the method shown in the embodiment of the present application provides a network coordination control device, which is used to improve the reliability of the two-stage current source inverter, thereby ensuring the stable operation of the network type weak power grid. The embodiment of the device corresponds to the aforementioned method embodiment. For the sake of ease of reading, this embodiment will no longer repeat the details of the aforementioned method embodiment one by one, but it should be clear that the device in this embodiment can correspond to all the contents of the aforementioned method embodiment. Specifically, Figure 3 As shown, a grid-type weak power grid is applied to deploy a two-stage current source inverter, wherein the two-stage current source inverter is composed of a first-stage step-down DC converter and a second-stage current source inverter in cascade connection, and the device includes:

[0082] An acquiring unit 31 is configured to acquire an active power error of the second-stage current source inverter and a freewheeling inductor current error of the first-stage step-down DC converter;

[0083] a processing unit 32 configured to process the active power error of the acquisition unit 31 using a proportional controller and the freewheeling inductor current error of the acquisition unit 31 using a proportional-integral controller in a parallel framework to obtain a three-phase voltage phase at a common coupling point, wherein the parallel framework is configured to represent a framework mode for synchronously processing the active power error and the freewheeling inductor current error;

[0084] The control unit 33 is used to coordinate the control of the two-stage current source inverter based on the three-phase voltage phase of the processing unit 32, so as to ensure the stable operation of the grid-type weak power grid.

[0085] Further, such as Figure 4 As shown, the control unit 33 includes:

[0086] a first determining module 331, configured to determine a three-phase current reference value at the common coupling point based on an active power error and a reactive power error of the second-stage current source inverter, and determine a freewheeling inductor current reference value of the first-stage step-down DC converter based on the three-phase current reference value at the common coupling point;

[0087] a second determining module 332, configured to determine a reference value of a d-axis DC component of the three-phase current at the common coupling point by using the three-phase current reference value and the three-phase voltage phase of the first determining module 331;

[0088] a third determining module 333, configured to determine a ripple function corresponding to the first-stage step-down DC converter according to the three-phase current d-axis DC component reference value of the second determining module 332 and the freewheeling inductor current reference value of the first determining module;

[0089] a fourth determining module 334, configured to obtain an average value of the bridge arm input voltage according to the fluctuation function of the third determining module 333 and the three-phase voltage amplitude reference value of the common coupling point;

[0090] A first processing module 335 is configured to process the DC link capacitor current error in the second-stage current source inverter using a proportional-integral controller to obtain a high-frequency voltage control component, wherein the high-frequency voltage control component is used to represent the voltage drop compensation corresponding to the first-stage step-down DC converter when the DC link capacitor current reference value is 0;

[0091] The calculation module 336 is used to calculate the reference duty cycle corresponding to the first-stage step-down DC converter by using the high-frequency voltage control component of the first processing module 335, the average value of the bridge arm input voltage of the fourth determination module 334, and the bridge arm input voltage sampling value, so as to coordinate the control of the two-stage current source inverter based on the reference duty cycle.

[0092] Further, such as Figure 4 As shown, the first determining module 331 is specifically configured to:

[0093] Using a proportional-integral controller to process the active power error and the reactive power error respectively, to obtain a three-phase voltage d-axis DC component reference value and a three-phase voltage q-axis DC component reference value at the common coupling point;

[0094] Obtaining a d-axis DC component error and a q-axis DC component error of the three-phase voltage at the common coupling point based on a d-axis DC component reference value of the three-phase voltage at the common coupling point and a sampled value of the d-axis DC component of the three-phase voltage at the common coupling point, as well as a q-axis DC component reference value of the three-phase voltage at the common coupling point and a sampled value of the q-axis DC component of the three-phase voltage at the common coupling point;

[0095] The three-phase voltage q-axis DC component error and the three-phase voltage d-axis DC component error are processed respectively by using a proportional-integral controller to obtain a three-phase current reference value of the common coupling point.

[0096] Further, such as Figure 4 As shown, the first determining module 331 is further configured to:

[0097] The unidirectional current reference value with the largest absolute value among the three-phase current reference values ​​is used as the freewheeling inductor current reference value of the first-stage step-down DC converter.

[0098] Further, such as Figure 4 As shown, the fourth determining module 334 is specifically configured to:

[0099] Calculating a three-phase voltage amplitude reference value at the common coupling point according to a three-phase voltage d-axis DC component reference value at the common coupling point and a three-phase voltage q-axis DC component reference value at the common coupling point;

[0100] The three-phase voltage amplitude reference value at the common coupling point and the fluctuation function are calculated using an instantaneous power method to obtain the average value of the bridge arm input voltage.

[0101] Further, such as Figure 4 As shown, the calculation module 336 is specifically used to:

[0102] Adding the high-frequency voltage control component and the input voltage average value to obtain a bridge arm input voltage reference value;

[0103] The ratio of the bridge arm input voltage reference value to the bridge arm input voltage sampling value is used as the reference duty cycle corresponding to the step-down DC converter;

[0104] The reference duty cycle is used to uniformly coordinate and control the first-stage step-down DC converter and the second-stage current source inverter, so as to ensure stable operation of the grid-type weak power grid.

[0105] Further, such as Figure 4 As shown, the device also includes:

[0106] a fifth determining module 337, configured to determine, after the second determining module 332, a q-axis DC component of the three-phase current at the point of common coupling using the three-phase current reference value and the three-phase voltage phase;

[0107] a sixth determining module 338, configured to obtain a d-axis DC component error of the three-phase current at the common coupling point and a q-axis DC component error of the three-phase current at the common coupling point based on the d-axis DC component reference value of the three-phase current at the common coupling point and the sampled value of the d-axis DC component of the three-phase current at the common coupling point from the second determining module 337, and the q-axis DC component reference value of the three-phase current at the common coupling point and the sampled value of the q-axis DC component of the three-phase current at the common coupling point from the fifth determining module 337;

[0108] The second processing module 339 is used to use a proportional-integral controller to process the three-phase current d-axis DC component error and the three-phase current q-axis DC component error of the sixth determination module 338 respectively, to obtain a three-phase current d-axis reference modulation wave and a three-phase current q-axis reference modulation wave, so as to perform pulse control on the second-stage current source inverter.

[0109] Furthermore, the embodiment of the present application also provides a storage medium, which is used to store a computer program, wherein when the computer program is running, the device where the storage medium is located is controlled to execute the above Figure 1-2 The network coordination control method described in .

[0110] Furthermore, the embodiment of the present application also provides a processor, which is used to run a program, wherein the program executes the above Figure 1-2 The network coordination control method described in .

[0111] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0112] It is understood that the relevant features of the above methods and devices can be referenced to each other. In addition, the terms "first" and "second" in the above embodiments are used to distinguish between the embodiments, and do not represent the advantages and disadvantages of the embodiments.

[0113] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0114] The algorithms and displays provided herein are not inherently related to any particular computer, virtual system, or other device. Various general-purpose systems may also be used together with the teachings herein. Based on the above description, it is apparent that the structure required for constructing such systems is suitable. In addition, the present application is not directed to any specific programming language. It should be understood that various programming languages ​​may be utilized to implement the present application described herein, and the description of the specific languages ​​above is provided for the purpose of disclosing the preferred embodiment of the present application.

[0115] In addition, the memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0116] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0117] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0118] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0119] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0120] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0121] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0122] Computer-readable media includes permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media (transitory media), such as modulated data signals and carrier waves.

[0123] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0124] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0125] The above are merely embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A network coordination control method, characterized in that: A method for deploying a grid-type weak power grid in which a two-stage current source inverter is deployed, wherein the two-stage current source inverter is composed of a first-stage step-down DC converter and a second-stage current source inverter in cascade connection, and the method comprises: Obtaining an active power error of the second-stage current source inverter and a freewheeling inductor current error of the first-stage step-down DC converter; In a parallel framework, a proportional controller is used to process the active power error, and a proportional-integral controller is used to process the freewheeling inductor current error to obtain a three-phase voltage phase at a common coupling point. The parallel framework is used to represent a framework mode for synchronously processing the active power error and the freewheeling inductor current error. Coordinated control of the two-stage current source inverter is performed based on the three-phase voltage phase and voltage drop compensation strategy to ensure stable operation of the grid-type weak power grid; Coordinated control of the two-stage current source inverter is performed based on the three-phase voltage phase and voltage drop compensation strategy, including: Determining a three-phase current reference value at the common coupling point based on an active power error and a reactive power error of the second-stage current source inverter, and determining a freewheeling inductor current reference value of the first-stage step-down DC converter based on the three-phase current reference value at the common coupling point; Determining a d-axis DC component reference value of the three-phase current at the common coupling point using the three-phase current reference value and the three-phase voltage phase; Determining a ripple function corresponding to the first-stage step-down DC converter according to the three-phase current d-axis DC component reference value and the freewheeling inductor current reference value; Obtaining an average value of the bridge arm input voltage according to the fluctuation function and a reference value of the three-phase voltage amplitude of the common coupling point; Processing a DC link capacitor current error in the second-stage current source inverter using a proportional-integral controller to obtain a high-frequency voltage control component, wherein the high-frequency voltage control component is used to represent a voltage drop compensation corresponding to the first-stage step-down DC converter when the DC link capacitor current reference value is 0; The reference duty cycle corresponding to the first-stage step-down DC converter is calculated using the high-frequency voltage control component, the average value of the bridge arm input voltage, and the bridge arm input voltage sampling value, so as to coordinately control the two-stage current source inverter based on the reference duty cycle.

2. The method according to claim 1, characterized in that Determining a three-phase current reference value of the common coupling point based on an active power error and a reactive power error of the second-stage current source inverter includes: Using a proportional-integral controller to process the active power error and the reactive power error respectively, to obtain a three-phase voltage d-axis DC component reference value and a three-phase voltage q-axis DC component reference value at the common coupling point; Obtaining a d-axis DC component error and a q-axis DC component error of the three-phase voltage at the common coupling point based on a d-axis DC component reference value of the three-phase voltage at the common coupling point and a sampled value of the d-axis DC component of the three-phase voltage at the common coupling point, as well as a q-axis DC component reference value of the three-phase voltage at the common coupling point and a sampled value of the q-axis DC component of the three-phase voltage at the common coupling point; The three-phase voltage q-axis DC component error and the three-phase voltage d-axis DC component error are processed respectively by using a proportional-integral controller to obtain a three-phase current reference value of the common coupling point.

3. The method according to claim 1, characterized in that The method further comprises: calculating a freewheeling inductor current reference value of the first-stage step-down DC converter based on the three-phase current reference value of the common coupling point, comprising: The unidirectional current reference value with the largest absolute value among the three-phase current reference values ​​is used as the freewheeling inductor current reference value of the first-stage step-down DC converter.

4. The method according to claim 2, characterized in that Obtaining an average value of the bridge arm input voltage using the fluctuation function and a three-phase voltage amplitude reference value of the common coupling point includes: Calculating a three-phase voltage amplitude reference value at the common coupling point according to a d-axis DC component reference value of the three-phase voltage at the common coupling point and a q-axis DC component reference value of the three-phase voltage at the common coupling point; The three-phase voltage amplitude reference value at the common coupling point and the fluctuation function are calculated using an instantaneous power method to obtain the average value of the bridge arm input voltage.

5. The method according to claim 1, wherein Calculating a reference duty cycle corresponding to the first-stage step-down DC converter using the high-frequency voltage control component, the average value of the bridge arm input voltage, and the bridge arm input voltage sampling value, so as to coordinately control the two-stage current source inverter based on the reference duty cycle, including: Adding the high-frequency voltage control component and the input voltage average value to obtain a bridge arm input voltage reference value; The ratio of the bridge arm input voltage reference value to the bridge arm input voltage sampling value is used as the reference duty cycle corresponding to the step-down DC converter; The reference duty cycle is used to uniformly coordinate and control the first-stage step-down DC converter and the second-stage current source inverter, so as to ensure stable operation of the grid-type weak power grid.

6. The method according to claim 1, wherein The method further comprises: Determining a q-axis DC component of the three-phase current at the common coupling point using the three-phase current reference value and the three-phase voltage phase; Obtaining a d-axis DC component error of the three-phase current at the common coupling point and a q-axis DC component error of the three-phase current at the common coupling point based on a d-axis DC component reference value of the three-phase current at the common coupling point and a sampled value of the d-axis DC component of the three-phase current at the common coupling point, as well as a q-axis DC component reference value of the three-phase current at the common coupling point and a sampled value of the q-axis DC component of the three-phase current at the common coupling point; A proportional-integral controller is used to process the three-phase current d-axis DC component error and the three-phase current q-axis DC component error respectively to obtain a three-phase current d-axis reference modulation wave and a three-phase current q-axis reference modulation wave to perform pulse control on the second-stage current source inverter.

7. A network coordination control device, characterized in that: A grid-type weak power grid is applied to deploy a two-stage current source inverter, wherein the two-stage current source inverter is composed of a first-stage step-down DC converter and a second-stage current source inverter in cascade connection, and the device includes: an acquiring unit, configured to acquire an active power error of the second-stage current source inverter and a freewheeling inductor current error of the first-stage step-down DC converter; a processing unit, configured to process the active power error of the acquisition unit using a proportional controller and the freewheeling inductor current error of the acquisition unit using a proportional-integral controller in a parallel framework to obtain a three-phase voltage phase at a common coupling point, wherein the parallel framework is configured to represent a framework mode for synchronously processing the active power error and the freewheeling inductor current error; A control unit, configured to coordinately control the two-stage current source inverter based on the three-phase voltage phase and voltage drop compensation strategy of the processing unit, so as to ensure stable operation of the grid-type weak power grid; The control unit comprises: a first determining module, configured to determine a three-phase current reference value at the common coupling point based on an active power error and a reactive power error of the second-stage current source inverter, and determine a freewheeling inductor current reference value of the first-stage step-down DC converter based on the three-phase current reference value of the common coupling point; a second determining module, configured to determine a reference value of a d-axis DC component of the three-phase current at the common coupling point by using the three-phase current reference value and the three-phase voltage phase of the first determining module; a third determining module, configured to determine a ripple function corresponding to the first-stage step-down DC converter according to the three-phase current d-axis DC component reference value of the second determining module and the freewheeling inductor current reference value of the first determining module; a fourth determining module, configured to obtain an average value of the bridge arm input voltage according to the fluctuation function of the third determining module and a reference value of the three-phase voltage amplitude of the common coupling point; a first processing module, configured to process a DC link capacitor current error in the second-stage current source inverter using a proportional-integral controller to obtain a high-frequency voltage control component, wherein the high-frequency voltage control component is used to represent a voltage drop compensation corresponding to the first-stage step-down DC converter when the DC link capacitor current reference value is 0; A calculation module is used to calculate the reference duty cycle corresponding to the first-stage step-down DC converter by using the high-frequency voltage control component of the first processing module, the average value of the bridge arm input voltage of the fourth determination module, and the bridge arm input voltage sampling value, so as to coordinately control the two-stage current source inverter based on the reference duty cycle.

8. A storage medium, characterized in that: The storage medium includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the networking coordination control method according to any one of claims 1 to 6.

9. A processor, characterized in that: The processor is used to run a program, wherein the program executes the networking coordination control method according to any one of claims 1 to 6 when running.

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