Modeling method and system of photovoltaic grid-forming inverter based on virtual synchronous machine control

Abstract

The present application relates to the field of grid-forming inverter control technology, and particularly relates to a photovoltaic grid-forming inverter modeling method and system based on virtual synchronous machine control, which comprises the following steps: constructing a typical power distribution network simulation scenario including a three-phase voltage source, a circuit breaker and a load; constructing a photovoltaic power generation system simulation model including a photovoltaic array, a Boost circuit, an MPPT model and a photovoltaic power generation system bypass switch; constructing a grid-forming inverter main circuit simulation model including a three-phase bridge circuit, a filter inductor, a filter capacitor and a circuit breaker; and constructing a grid-forming inverter control circuit simulation model including an enable signal trigger, a virtual synchronous machine control module and an SVPWM modulation module; wherein the virtual synchronous machine control module uses reactive power regulation to control the output voltage amplitude of the grid-forming inverter, uses active power regulation to control the output voltage phase of the grid-forming inverter, and adds a direct current side voltage control loop outside the active power regulation loop.

Description

Technical Field

[0001] This invention relates to the field of grid-connected inverter control technology, and in particular to a modeling method and system for photovoltaic grid-connected inverters based on virtual synchronous machine control. Background Technology

[0002] Large-scale wind and solar renewable energy generation, through grid connection with power electronic equipment, is gradually replacing traditional synchronous generators. However, the lack of rotational inertia in power electronic converters results in relatively low inertia and poor stability in the new power system. Currently, most wind and solar renewable energy grid connections use grid-following converters with current source control mode. These converters synchronize with the grid by measuring the phase at the grid connection point using a phase-locked loop (PLL). This approach leads to poor stability in grids with low system strength and low physical inertia. Therefore, grid-based control is more suitable for converters. Grid-based converters use voltage source control mode, and their power synchronization strategy is similar to that of synchronous generators. They do not require PLL synchronization with the grid and possess a certain degree of autonomous support capability.

[0003] PSCAD / EMTDC is an electromagnetic transient simulation software. Currently, there are few simulation modeling methods for photovoltaic grid-connected inverters based on PSCAD / EMTDC. However, grid-connected control still requires more in-depth research on synchronous stability, current limiting protection, fault ride-through, and islanded / grid-connected mode switching. There is an urgent need for a general and universal simulation modeling method for photovoltaic grid-connected inverters to provide a foundation for subsequent research on grid-connected control.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] This invention provides a modeling method and system for photovoltaic grid-type inverters based on virtual synchronous machine control, thereby effectively solving the problems in the background technology.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a modeling method for photovoltaic grid-connected inverters based on virtual synchronous machine control, comprising the following steps:

[0007] Construct a typical power distribution network simulation scenario that includes three-phase voltage sources, circuit breakers, and loads;

[0008] A simulation model of a photovoltaic power generation system is constructed, including a photovoltaic array, a Boost circuit, an MPPT model, and a bypass switch for the photovoltaic power generation system.

[0009] Construct a simulation model of the main circuit of a grid-type inverter, including a three-phase bridge circuit, filter inductors, filter capacitors, and circuit breakers;

[0010] Based on the typical power distribution network simulation scenario, photovoltaic power generation system simulation model, and grid-type inverter main circuit simulation model, a grid-type inverter control circuit simulation model is constructed, including enable signal triggering, virtual synchronous machine control module, and SVPWM modulation module.

[0011] The virtual synchronous machine control module uses reactive power regulation to control the output voltage amplitude of the grid-type inverter and active power regulation to control the output voltage phase of the grid-type inverter. A DC-side voltage control loop is added to the outer loop of the active power regulation loop.

[0012] Furthermore, the Boost circuit includes a DC filter capacitor, a DC bus support capacitor, a boost inductor, an IGBT switching transistor, and a diode. The IGBT switching transistor is controlled to turn on or off by the turn-on signal generated by the MPPT model PWM.

[0013] Furthermore, the MPPT model includes:

[0014] The output voltage and output current of the photovoltaic array are collected at the sampling frequency value and differentiated to obtain the output differential voltage dV and output differential current dI of the photovoltaic array;

[0015] The output differential voltage dV of the photovoltaic array is multiplied by the output current I of the photovoltaic array, and then added to the product of the output differential current dI and the output voltage V of the photovoltaic array. This product is then multiplied by the output differential voltage dV of the photovoltaic array. The resulting value is passed through a range comparator. When the multiplier is lower than the lower limit of the input, the output is -1. When the multiplier is between the upper and lower limits of the input, the output is 0. When the multiplier is higher than the upper limit of the input, the output is 1.

[0016] The output value is then multiplied by the switch signal on, then by -1, then by the time constant add, and finally integrated to obtain D. D is then compared with the triangular carrier wave to obtain the IGBT turn-on signal g, which is used for maximum power point tracking of photovoltaic power generation.

[0017] Furthermore, in the simulation model of the main circuit of the grid-type inverter, the three-phase bridge circuit consists of 6 IGBTs and anti-parallel diodes. The IGBTs of the three-phase bridge circuit are triggered to turn on or off by 6 PWM signals P1, P2, P3, P4, P5, and P6.

[0018] The main circuit of the grid-type inverter uses an LC filter for filtering, and the circuit breaker determines whether the grid-type inverter is connected to or disconnected from the distribution network.

[0019] Furthermore, in the simulation model of the grid-connected inverter control circuit, the input signals of the virtual synchronous machine control module include: the grid-connected voltage Vsh of the photovoltaic inverter, the effective value of the grid-connected voltage Vshrms of the photovoltaic inverter, the current IL flowing through the inverter filter inductor, and the grid-connected current Ish of the photovoltaic inverter.

[0020] The output signal includes a reference voltage, which is modulated by SVPWM with the DC side voltage Udc of the photovoltaic inverter to obtain the IGBT turn-on signal;

[0021] The virtual synchronous machine control module includes: a DQ conversion module, a DQ inverse conversion module, a power calculation module, and a control loop.

[0022] Furthermore, the virtual synchronous machine control module uses reactive power regulation to control the output voltage amplitude of the grid-connected inverter and active power regulation to control the output voltage phase of the grid-connected inverter, including:

[0023] The grid-connected voltage Vsh of the photovoltaic inverter is transformed by DQ to obtain the d-axis component Vshd and the q-axis component Vshq of the grid-connected voltage; the grid-connected current Ish of the photovoltaic inverter is transformed by DQ to obtain the d-axis component Ishd and the q-axis component Ishq of the grid-connected current.

[0024] The obtained electrical quantities are used to calculate power and then filtered to obtain the active power P and reactive power Q of the grid-type inverter output.

[0025] After passing through the Enable signal and the PI controller, the voltage amplitude of the transformer area is added to obtain the reference effective value of the grid-connected voltage VshRefRms of the photovoltaic inverter.

[0026] Based on the reference value of the active power output of the grid-type inverter and the active power output P, ​​the active power difference PError is obtained. Based on the active power difference PError and the reference angular velocity of the distribution network, the phase angle theta of the output voltage of the grid-type inverter is obtained, and feedback control is performed.

[0027] The reference value of the output voltage VshRef of the grid-connected inverter is calculated based on the effective reference value of the output voltage VshRefRms and the phase angle theta of the output voltage of the grid-connected inverter.

[0028] The DQ transformation of the grid-connected inverter output voltage reference value VshRef yields the d-axis component VshdRef and the q-axis component VshqRef of the grid-connected inverter output voltage reference value.

[0029] The grid-connected inverter output voltage reference value d-axis component Vshd is obtained by subtracting the grid-connected inverter output voltage d-axis component Vshd from the grid-connected inverter output voltage reference value d-axis component VrdRef after passing through the enable signal and PI control; the grid-connected inverter output voltage reference value q-axis component VrqRef is obtained by subtracting the grid-connected inverter output voltage d-axis component Vshq from the grid-connected inverter output voltage reference value q-axis component VrqRef after passing through the enable signal and PI control.

[0030] The modulation voltage is obtained by performing DQ inverse transformation on the d-axis component VrdRef of the modulation voltage reference value output by the grid-type inverter and the q-axis component VrqRef of the modulation voltage reference value output by the grid-type inverter.

[0031] The present invention also includes a photovoltaic grid-type inverter modeling system based on virtual synchronous machine control, using the method described above, the system comprising:

[0032] Typical scenario modeling unit, used to construct typical distribution network simulation scenarios including three-phase voltage sources, circuit breakers and loads;

[0033] The photovoltaic modeling unit is used to construct a photovoltaic power generation system simulation model, including a photovoltaic array, a Boost circuit, an MPPT model, and a photovoltaic power generation system bypass switch.

[0034] The inverter main circuit modeling unit is used to construct a network-type inverter main circuit simulation model that includes a three-phase bridge circuit, filter inductors, filter capacitors, and circuit breakers.

[0035] The inverter control circuit modeling unit is used to construct a grid-type inverter control circuit simulation model, including an enable signal trigger, a virtual synchronous machine control module, and an SVPWM modulation module, based on the typical distribution network simulation scenario, the photovoltaic power generation system simulation model, and the grid-type inverter main circuit simulation model.

[0036] The virtual synchronous machine control module uses reactive power regulation to control the output voltage amplitude of the grid-type inverter and active power regulation to control the output voltage phase of the grid-type inverter. A DC-side voltage control loop is added to the outer loop of the active power regulation loop.

[0037] The present invention also includes a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the method as described above.

[0038] The present invention also includes a storage medium having a computer program stored thereon, which, when executed by a processor, implements the method as described above.

[0039] The beneficial effects of this invention are as follows: Photovoltaic power generation and grid-connected inverters are built on PSCAD / EMTDC respectively, which facilitates subsequent research on control strategies, protection strategies, impact on weak power grids, and islanded / grid-connected mode switching of photovoltaic grid-connected inverters on PSCAD / EMTDC; a virtual synchronous machine control loop is constructed on PSCAD / EMTDC, using reactive power regulation to control the inverter output voltage amplitude and active power regulation to control the inverter output voltage phase. A DC-side voltage control loop is added to the outer loop of the active power regulation loop to stabilize the photovoltaic power generation and inverter DC-side voltage, reducing the impact of photovoltaic power generation fluctuations on the inverter. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a flowchart of the method in Example 1;

[0042] Figure 2 This is a schematic diagram of the system structure in Example 1;

[0043] Figure 3 This is the simulation model of the photovoltaic grid-type inverter based on virtual synchronous machine control in Example 2;

[0044] Figure 4 This is a typical power distribution network simulation model in Example 2;

[0045] Figure 5 This is the simulation model of the photovoltaic power generation system in Example 2;

[0046] Figure 6 This is the photovoltaic array simulation model in Example 2;

[0047] Figure 7 This is the simulation model of the Boost circuit in Example 2;

[0048] Figure 8 This refers to the MPPT simulation model in Example 2;

[0049] Figure 9 This is the simulation model of the main circuit of the grid-type inverter in Example 2;

[0050] Figure 10 This is the simulation model of the overall control circuit of the grid-type inverter in Example 2;

[0051] Figure 11 This is the simulation model of the virtual synchronous machine control DQ transformation module in Example 2;

[0052] Figure 12 This is a simulation model of the virtual synchronous machine control power calculation module in Example 2;

[0053] Figure 13 This is a simulation model of the reactive power-voltage control loop of the virtual synchronous machine control in Example 2;

[0054] Figure 14 This is the simulation model of the active-frequency control loop of the virtual synchronous machine control in Example 2;

[0055] Figure 15 This is a simulation model of the output voltage reference value of the grid-type inverter in Example 2;

[0056] Figure 16 This is a simulation model of the DQ transformation of the output voltage reference value of the grid-type inverter in Example 2;

[0057] Figure 17 This is a simulation model of the output modulation voltage of the grid-type inverter in Example 2;

[0058] Figure 18 This is the simulation model of the inverse DQ transformation of the modulation voltage of the grid-type inverter in Example 2;

[0059] Figure 19 This is a schematic diagram of the structure of the computer device of the present invention. Detailed Implementation

[0060] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0061] Example 1:

[0062] like Figure 1 The following is a modeling method for a photovoltaic grid-connected inverter based on virtual synchronous machine control, comprising the following steps:

[0063] Construct a typical power distribution network simulation scenario that includes three-phase voltage sources, circuit breakers, and loads;

[0064] A simulation model of a photovoltaic power generation system is constructed, including a photovoltaic array, a Boost circuit, an MPPT model, and a bypass switch for the photovoltaic power generation system.

[0065] Construct a simulation model of the main circuit of a grid-type inverter, including a three-phase bridge circuit, filter inductors, filter capacitors, and circuit breakers;

[0066] Based on typical power distribution network simulation scenarios, photovoltaic power generation system simulation models, and grid-type inverter main circuit simulation models, a grid-type inverter control circuit simulation model is constructed, including enable signal triggering, virtual synchronous machine control module, and SVPWM modulation module.

[0067] The virtual synchronous machine control module uses reactive power regulation to control the output voltage amplitude of the grid-type inverter and active power regulation to control the output voltage phase of the grid-type inverter. A DC-side voltage control loop is added to the outer loop of the active power regulation loop.

[0068] Photovoltaic power generation and grid-connected inverters were built on PSCAD / EMTDC, which facilitates subsequent research on control strategies, protection strategies, impact on weak grids, and islanded / grid-connected mode switching of photovoltaic grid-connected inverters on PSCAD / EMTDC. A control loop for virtual synchronous machine control was constructed on PSCAD / EMTDC, using reactive power regulation to control the inverter output voltage amplitude and active power regulation to control the inverter output voltage phase. A DC-side voltage control loop was added to the outer loop of the active power regulation loop to stabilize the DC-side voltage of photovoltaic power generation and inverter, reducing the impact of photovoltaic power generation fluctuations on the inverter.

[0069] In this embodiment, the Boost circuit includes a DC filter capacitor, a DC bus support capacitor, a boost inductor, an IGBT switch, and a diode. The IGBT switch is controlled to turn on or off by a turn-on signal generated by the MPPT model PWM.

[0070] The MPPT model includes:

[0071] The output voltage and output current of the photovoltaic array are collected at the sampling frequency value and differentiated to obtain the output differential voltage dV and output differential current dI of the photovoltaic array;

[0072] The output differential voltage dV of the photovoltaic array is multiplied by the output current I of the photovoltaic array, and then added to the product of the output differential current dI and the output voltage V of the photovoltaic array. This product is then multiplied by the output differential voltage dV of the photovoltaic array. The resulting value is passed through a range comparator. When the multiplier is lower than the lower limit of the input, the output is -1. When the multiplier is between the upper and lower limits of the input, the output is 0. When the multiplier is higher than the upper limit of the input, the output is 1.

[0073] The output value is then multiplied by the switch signal on, then by -1, then by the time constant add, and finally integrated to obtain D. D is then compared with the triangular carrier wave to obtain the IGBT turn-on signal g, which is used for maximum power point tracking of photovoltaic power generation.

[0074] In the simulation model of the main circuit of the grid-type inverter, the three-phase bridge circuit consists of 6 IGBTs and anti-parallel diodes. The IGBTs of the three-phase bridge circuit are triggered to turn on or off by 6 PWM signals P1, P2, P3, P4, P5, and P6.

[0075] The main circuit of the grid-type inverter uses an LC filter for filtering, and the circuit breaker determines whether the grid-type inverter is connected to or disconnected from the distribution network.

[0076] As a preferred embodiment of the above, in the simulation model of the grid-connected inverter control circuit, the input signals of the virtual synchronous machine control module include: the grid-connected voltage Vsh of the photovoltaic inverter, the effective value of the grid-connected voltage Vshrms of the photovoltaic inverter, the current IL flowing through the inverter filter inductor, and the grid-connected current Ish of the photovoltaic inverter.

[0077] The output signal includes a reference voltage, which is modulated by SVPWM with the DC side voltage Udc of the photovoltaic inverter to obtain the IGBT turn-on signal;

[0078] The virtual synchronous machine control module includes: a DQ conversion module, a DQ inverse conversion module, a power calculation module, and a control loop.

[0079] In this embodiment, the virtual synchronous machine control module uses reactive power regulation to control the output voltage amplitude of the grid-connected inverter and active power regulation to control the output voltage phase of the grid-connected inverter, including:

[0080] The grid-connected voltage Vsh of the photovoltaic inverter is transformed by DQ to obtain the d-axis component Vshd and the q-axis component Vshq of the grid-connected voltage; the grid-connected current Ish of the photovoltaic inverter is transformed by DQ to obtain the d-axis component Ishd and the q-axis component Ishq of the grid-connected current.

[0081] The obtained electrical quantities are used to calculate power and then filtered to obtain the active power P and reactive power Q of the grid-type inverter output.

[0082] After passing through the Enable signal and the PI controller, the voltage amplitude of the transformer area is added to obtain the reference effective value of the grid-connected voltage VshRefRms of the photovoltaic inverter.

[0083] Based on the reference value of the active power output of the grid-type inverter and the active power output P, ​​the active power difference PError is obtained. Based on the active power difference PError and the reference angular velocity of the distribution network, the phase angle theta of the output voltage of the grid-type inverter is obtained, and feedback control is performed.

[0084] The reference value of the output voltage VshRef of the grid-connected inverter is calculated based on the effective reference value of the output voltage VshRefRms and the phase angle theta of the output voltage of the grid-connected inverter.

[0085] The DQ transformation of the grid-connected inverter output voltage reference value VshRef yields the d-axis component VshdRef and the q-axis component VshqRef of the grid-connected inverter output voltage reference value.

[0086] The grid-connected inverter output voltage reference value d-axis component Vshd is obtained by subtracting the grid-connected inverter output voltage d-axis component Vshd from the grid-connected inverter output voltage reference value d-axis component VrdRef after passing through the enable signal and PI control; the grid-connected inverter output voltage reference value q-axis component VrqRef is obtained by subtracting the grid-connected inverter output voltage d-axis component Vshq from the grid-connected inverter output voltage reference value q-axis component VrqRef after passing through the enable signal and PI control.

[0087] The modulation voltage is obtained by performing DQ inverse transformation on the d-axis component VrdRef of the modulation voltage reference value output by the grid-type inverter and the q-axis component VrqRef of the modulation voltage reference value output by the grid-type inverter.

[0088] like Figure 2 As shown, this embodiment also includes a photovoltaic grid-type inverter modeling system based on virtual synchronous machine control, using the method described above. The system includes:

[0089] Typical scenario modeling unit, used to construct typical distribution network simulation scenarios including three-phase voltage sources, circuit breakers and loads;

[0090] The photovoltaic modeling unit is used to construct a photovoltaic power generation system simulation model, including a photovoltaic array, a Boost circuit, an MPPT model, and a photovoltaic power generation system bypass switch.

[0091] The inverter main circuit modeling unit is used to construct a network-type inverter main circuit simulation model that includes a three-phase bridge circuit, filter inductors, filter capacitors, and circuit breakers.

[0092] The inverter control circuit modeling unit is used to construct a grid-type inverter control circuit simulation model, including enable signal triggering, virtual synchronous machine control module and SVPWM modulation module, based on typical distribution network simulation scenarios, photovoltaic power generation system simulation models and grid-type inverter main circuit simulation models.

[0093] The virtual synchronous machine control module uses reactive power regulation to control the output voltage amplitude of the grid-type inverter and active power regulation to control the output voltage phase of the grid-type inverter. A DC-side voltage control loop is added to the outer loop of the active power regulation loop.

[0094] Example 2:

[0095] This embodiment includes a simulation modeling method for a photovoltaic grid-connected inverter based on virtual synchronous machine control, the process of which is shown below:

[0096] S1: Construct a typical power distribution network simulation scenario;

[0097] S2: Construct a simulation model of a photovoltaic power generation system;

[0098] S3: Construct a simulation model of the main circuit of a grid-type inverter;

[0099] S4: Construct a simulation model of the grid-type inverter control circuit.

[0100] Simulation model of photovoltaic grid-type inverter based on virtual synchronous machine control, as follows: Figure 3 As shown, the detailed process of the simulation modeling method is as follows:

[0101] S1: Construct a typical power distribution network simulation scenario. A typical power distribution network simulation model is as follows: Figure 4 As shown in Table 1, a typical distribution network simulation model mainly consists of a three-phase voltage source, circuit breakers, and loads. The circuit breakers can simulate islanded / connected network scenarios. Typical distribution network parameter settings are shown in Table 1.

[0102] Table 1. Main parameter settings for a typical power distribution network simulation model

[0103]

[0104] S2: Construct a simulation model of the photovoltaic power generation system. The photovoltaic power generation system simulation model is as follows: Figure 5 As shown, it consists of a photovoltaic array, Boost circuit, MPPT model, and photovoltaic power generation system bypass switch, which are included in the PSCAD / EMTDC simulation software.

[0105] Photovoltaic array simulation model such as Figure 6 As shown in Table 2, the parameter settings are as follows.

[0106] Table 2 Photovoltaic Array Parameter Settings

[0107]

[0108] Boost circuit simulation model such as Figure 7As shown, it mainly consists of a DC filter capacitor, a DC bus support capacitor, a boost inductor, an IGBT, and diodes. The IGBT switching transistor requires a turn-on signal generated by the MPPT model PWM to control its turn-on or turn-off. Parameter settings are shown in Table 3.

[0109] Table 3 Boost Circuit Parameter Settings

[0110]

[0111] MPPT simulation model such as Figure 8 As shown, the input terminals are the photovoltaic array output voltage Vpv and the photovoltaic array output current Ipv. The sampling frequency is obtained by dividing the constant 1.0 by the time constant Ts = 0.0001. The photovoltaic array output voltage and current are collected at this sampling frequency and differentiated to obtain the photovoltaic array output differential voltage dV and photovoltaic array output differential current dI. The photovoltaic array output differential voltage dV is multiplied by the photovoltaic array output current I, and the product of the photovoltaic array output differential current dI and the photovoltaic array output voltage V. This product is then multiplied again by the photovoltaic array output differential voltage dV. The resulting value is passed through a range comparator. When the multiplier is lower than the lower limit of the input, the output is -1; when the multiplier is between the upper and lower limits of the input, the output is 0; and when the multiplier is higher than the upper limit of the input, the output is 1. The output value is then multiplied by the switch signal on, then by -1, then by the time constant add, and finally integrated to obtain D. D is then compared with a triangular carrier wave to obtain the IGBT trigger signal g, which is used to achieve maximum power point tracking (MPPT) of the photovoltaic power generation.

[0112] S3: Construct a simulation model of the main circuit of a grid-connected inverter. The simulation model of the main circuit of a grid-connected inverter is as follows: Figure 9 As shown in Table 4, the simulation model of the main circuit of the grid-connected inverter consists of a three-phase bridge circuit with six IGBTs and anti-parallel diodes, a filter inductor, a filter capacitor, and a circuit breaker. The IGBTs in the three-phase bridge circuit are triggered to turn on or off by six PWM signals P1, P2, P3, P4, P5, and P6. The main circuit of the grid-connected inverter uses an LC filter for filtering, and the circuit breaker determines whether the grid-connected inverter connects to or disconnects from the power distribution network. The parameter settings for the main circuit of the grid-connected inverter are shown in Table 4.

[0113] Table 4 Main Circuit Parameter Settings for Grid-Type Inverters

[0114]

[0115] S4: Construct a simulation model of the grid-connected inverter control circuit. The overall control circuit simulation model of the grid-connected inverter is as follows: Figure 10As shown, the simulation model of the overall control circuit of the grid-connected inverter mainly includes an enable signal trigger, a virtual synchronous machine control module, and an SVPWM modulation module. The input signals of the virtual synchronous machine control module include the photovoltaic inverter grid-connected point voltage Vsh, the effective value of the photovoltaic inverter grid-connected point voltage Vshrms, the current IL flowing through the inverter filter inductor, and the photovoltaic inverter grid-connected point current Ish; the output signal is a reference voltage, which, along with the photovoltaic inverter DC-side voltage Udc, is modulated by SVPWM to obtain the IGBT turn-on signal.

[0116] The virtual synchronous machine control module of the grid-type photovoltaic inverter mainly consists of a DQ conversion module, a DQ inverse conversion module, a power calculation module, and a control loop. The modeling method of the virtual synchronous machine control module will be described in detail below.

[0117] First, DQ transformation is performed on the grid-connected voltage Vsh and grid-connected current Ish of the photovoltaic inverter to obtain the d-axis component Vshd and q-axis component Vshq of the grid-connected voltage; and the d-axis component Ishd and q-axis component Ishq of the grid-connected current. Figure 11 As shown.

[0118] The obtained electrical quantities are used for power calculation. The d-axis component of the grid-connected point voltage Vshd is multiplied by the d-axis component of the grid-connected point current Ishd, and the q-axis component of the grid-connected point voltage Vshq is multiplied by the q-axis component of the grid-connected point current Ishq. The two multipliers are added together, multiplied by 1.5, and then filtered to obtain the active power P output of the grid-connected inverter. The d-axis component of the grid-connected point voltage Vshd is multiplied by the q-axis component of the grid-connected point current Ishq, and the two multipliers are subtracted, multiplied by 1.5, and then filtered to obtain the reactive power Q output of the grid-connected inverter. Figure 12 As shown.

[0119] Divide the effective value of the grid-connected voltage Vshrms of the photovoltaic inverter by Multiply by Then, subtract the phase voltage amplitude U*0.310269 from the voltage level, multiply by 1 after passing the enable signal, add this to the difference between the reference reactive power Q* and the output reactive power Q of the grid-connected inverter, pass through the enable signal again, and after passing through the PI controller, add this to the voltage level U* to obtain the reference effective value VshRefRms of the photovoltaic inverter grid connection point voltage. The reactive power-voltage control loop is as follows: Figure 13 As shown.

[0120] like Figure 14As shown, the reference value Udc* of the DC side voltage of the grid-connected inverter is subtracted from the actual value Udc of the DC side voltage of the grid-connected inverter. After passing through the enable signal Enable and then through PI control, the result is multiplied by the active power Ppv output by the photovoltaic array. This multiplier is added to the reference value P* of the active power output of the grid-connected inverter, and then subtracted from the active power P of the grid-connected inverter to obtain the active power difference PError. 2 Multiplying by the frequency of 50 gives the distribution network reference angular velocity wn. Subtracting this from the grid-connected inverter's output voltage angular velocity w, and then multiplying by 1 after passing through the enable signal (Enable), this is added to the active power difference PError. The result is then divided by the distribution network reference angular velocity wn and subjected to feedback control. This is done by subtracting the value obtained by multiplying by 0.01 after the enable signal and integrating it (twice the result), and then adding this to the distribution network reference angular velocity wn to obtain the grid-connected inverter's output voltage angular velocity w. Finally, the grid-connected inverter's output voltage angular velocity w is divided by 2. The output voltage frequency f of the grid-connected inverter is obtained; the output voltage angular velocity w of the grid-connected inverter is integrated after passing through the enable signal Enable to obtain the output voltage phase angle theta of the grid-connected inverter.

[0121] The reference effective value of the grid-connected inverter output voltage VshRefRms is compared with the phase angle theta of the grid-connected inverter output voltage. and Multiplying the sine values ​​yields the output voltage reference value VshRef of the grid-connected inverter, such as... Figure 15 As shown.

[0122] The DQ transformation is performed on the output voltage reference value VshRef of the grid-connected inverter to obtain the d-axis component VshdRef and the q-axis component VshqRef of the output voltage reference value of the grid-connected inverter, as follows: Figure 16 As shown.

[0123] like Figure 17 As shown, the d-axis component of the grid-connected inverter output voltage Vshd is subtracted from the d-axis component Vshd of the grid-connected inverter output voltage reference value. After passing through the enable signal and PI control, the d-axis component VrdRef of the grid-connected inverter output modulation voltage reference value is obtained. Similarly, the q-axis component VshqRef of the grid-connected inverter output voltage reference value Vrq is subtracted from the d-axis component Vshq of the grid-connected inverter output voltage reference value. After passing through the enable signal and PI control, the q-axis component VrqRef of the grid-connected inverter output modulation voltage reference value is obtained.

[0124] The modulation voltage is obtained by performing an inverse DQ transform on the d-axis component VrdRef of the grid-connected inverter output modulation voltage reference value and the q-axis component VrqRef of the grid-connected inverter output modulation voltage reference value, such as... Figure 18As shown.

[0125] Please see Figure 19 The diagram shows a structural schematic of a computer device provided in an embodiment of this application. An embodiment of this application provides a computer device 400, including a processor 410 and a memory 420. The memory 420 stores a computer program executable by the processor 410. When the computer program is executed by the processor 410, it performs the method described above.

[0126] This application embodiment also provides a storage medium 430, on which a computer program is stored, and the computer program is executed by a processor 410 to perform the above method.

[0127] The storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0128] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. "A plurality of" means two or more, unless otherwise explicitly specified.

[0129] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0130] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions 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 suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0131] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0132] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0133] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0134] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0135] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A modeling method for photovoltaic grid-connected inverters based on virtual synchronous machine control, characterized in that, Includes the following steps: Construct a typical power distribution network simulation scenario that includes three-phase voltage sources, circuit breakers, and loads; A simulation model of a photovoltaic power generation system is constructed, including a photovoltaic array, a Boost circuit, an MPPT model, and a bypass switch for the photovoltaic power generation system. Construct a simulation model of the main circuit of a grid-type inverter, including a three-phase bridge circuit, filter inductors, filter capacitors, and circuit breakers; Based on the typical power distribution network simulation scenario, photovoltaic power generation system simulation model, and grid-type inverter main circuit simulation model, a grid-type inverter control circuit simulation model is constructed, including enable signal triggering, virtual synchronous machine control module, and SVPWM modulation module. The virtual synchronous machine control module uses reactive power regulation to control the output voltage amplitude of the grid-type inverter, and active power regulation to control the output voltage phase of the grid-type inverter. A DC-side voltage control loop is added to the outer loop of the active power regulation loop. In the simulation model of the grid-connected inverter control circuit, the input signals of the virtual synchronous machine control module include: the grid-connected voltage Vsh of the photovoltaic inverter, the effective value of the grid-connected voltage Vshrms of the photovoltaic inverter, the current IL flowing through the inverter filter inductor, and the grid-connected current Ish of the photovoltaic inverter. The output signal includes a reference voltage, which is modulated by SVPWM with the DC side voltage Udc of the photovoltaic inverter to obtain the IGBT turn-on signal; The virtual synchronous machine control module includes: a DQ conversion module, a DQ inverse conversion module, a power calculation module, and a control loop; The virtual synchronous machine control module uses reactive power regulation to control the output voltage amplitude of the grid-connected inverter and active power regulation to control the output voltage phase of the grid-connected inverter, including: The grid-connected voltage Vsh of the photovoltaic inverter is transformed by DQ to obtain the d-axis component Vshd and the q-axis component Vshq of the grid-connected voltage; the grid-connected current Ish of the photovoltaic inverter is transformed by DQ to obtain the d-axis component Ishd and the q-axis component Ishq of the grid-connected current. The obtained electrical quantities are used to calculate power and then filtered to obtain the active power P and reactive power Q of the grid-type inverter output. After passing through the Enable signal and the PI controller, the voltage amplitude of the transformer area is added to obtain the reference effective value of the grid-connected voltage VshRefRms of the photovoltaic inverter. Based on the reference value of the active power output of the grid-type inverter and the active power output P, ​​the active power difference PError is obtained. Based on the active power difference PError and the reference angular velocity of the distribution network, the phase angle theta of the output voltage of the grid-type inverter is obtained, and feedback control is performed. The reference value of the output voltage VshRef of the grid-connected inverter is calculated based on the effective reference value of the output voltage VshRefRms and the phase angle theta of the output voltage of the grid-connected inverter. The DQ transformation of the grid-connected inverter output voltage reference value VshRef yields the d-axis component VshdRef and the q-axis component VshqRef of the grid-connected inverter output voltage reference value. The grid-connected inverter output voltage reference value d-axis component Vshd is obtained by subtracting the grid-connected inverter output voltage d-axis component Vshd from the grid-connected inverter output voltage reference value d-axis component VrdRef after passing through the enable signal and PI control; the grid-connected inverter output voltage reference value q-axis component VrqRef is obtained by subtracting the grid-connected inverter output voltage d-axis component Vshq from the grid-connected inverter output voltage reference value q-axis component VrqRef after passing through the enable signal and PI control. The modulation voltage is obtained by performing DQ inverse transformation on the d-axis component VrdRef of the modulation voltage reference value output by the grid-type inverter and the q-axis component VrqRef of the modulation voltage reference value output by the grid-type inverter.

2. The photovoltaic grid-type inverter modeling method based on virtual synchronous machine control according to claim 1, characterized in that, The Boost circuit includes a DC filter capacitor, a DC bus support capacitor, a boost inductor, an IGBT switching transistor, and a diode. The IGBT switching transistor is controlled to turn on or off by the conduction signal generated by the MPPT model PWM.

3. The photovoltaic grid-type inverter modeling method based on virtual synchronous machine control according to claim 2, characterized in that, The MPPT model includes: The output voltage and output current of the photovoltaic array are collected at the sampling frequency value and differentiated to obtain the output differential voltage dV and output differential current dI of the photovoltaic array; The output differential voltage dV of the photovoltaic array is multiplied by the output current I of the photovoltaic array, and then added to the product of the output differential current dI and the output voltage V of the photovoltaic array. This product is then multiplied by the output differential voltage dV of the photovoltaic array. The resulting value is passed through a range comparator. When the multiplier is lower than the lower limit of the input, the output is -1. When the multiplier is between the upper and lower limits of the input, the output is 0. When the multiplier is higher than the upper limit of the input, the output is 1. The output value is then multiplied by the switch signal on, then by -1, then by the time constant add, and finally integrated to obtain D. D is then compared with the triangular carrier wave to obtain the IGBT turn-on signal g, which is used for maximum power point tracking of photovoltaic power generation.

4. The photovoltaic grid-type inverter modeling method based on virtual synchronous machine control according to claim 1, characterized in that, In the simulation model of the main circuit of the grid-type inverter, the three-phase bridge circuit consists of 6 IGBTs and anti-parallel diodes. The IGBTs of the three-phase bridge circuit are triggered to turn on or off by 6 PWM signals P1, P2, P3, P4, P5, and P6. The main circuit of the grid-type inverter uses an LC filter for filtering, and the circuit breaker determines whether the grid-type inverter is connected to or disconnected from the distribution network.

5. A photovoltaic grid-type inverter modeling system based on virtual synchronous machine control, characterized in that, Using the method as described in any one of claims 1 to 4, the system comprises: Typical scenario modeling unit, used to construct typical distribution network simulation scenarios including three-phase voltage sources, circuit breakers and loads; The photovoltaic modeling unit is used to construct a photovoltaic power generation system simulation model, including a photovoltaic array, a Boost circuit, an MPPT model, and a photovoltaic power generation system bypass switch. The inverter main circuit modeling unit is used to construct a network-type inverter main circuit simulation model that includes a three-phase bridge circuit, filter inductors, filter capacitors, and circuit breakers. The inverter control circuit modeling unit is used to construct a grid-type inverter control circuit simulation model, including an enable signal trigger, a virtual synchronous machine control module, and an SVPWM modulation module, based on the typical distribution network simulation scenario, the photovoltaic power generation system simulation model, and the grid-type inverter main circuit simulation model. The virtual synchronous machine control module uses reactive power regulation to control the output voltage amplitude of the grid-type inverter and active power regulation to control the output voltage phase of the grid-type inverter. A DC-side voltage control loop is added to the outer loop of the active power regulation loop.

6. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in any one of claims 1-4.

7. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the method as described in any one of claims 1-4.

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