A virtual inertia adaptive control method and device for a network converter

Abstract

This invention discloses a virtual inertia adaptive control method for grid-connected converters, relating to the field of novel power system control technology. In the context of novel power systems with a high proportion of renewable energy, based on a system voltage state monitoring model, it accurately determines the system operating state and calculates the optimal active and reactive power reference values ​​for the grid-connected converter, achieving optimal support configuration of the grid-connected converter for system frequency. This invention also discloses a device based on the virtual inertia adaptive control method for grid-connected converters. Based on the converter's virtual inertia adaptive control system, it performs local virtual inertia adaptive adjustment under different operating states, accurately tracks the given power reference value, and achieves optimal response control of the converter's active and reactive power. This invention improves the frequency response characteristics of novel power systems and enhances the system's safety and stability margin under different operating states.

Description

Technical Field

[0001] This invention relates to the field of novel power system control technology, and in particular to a virtual inertia adaptive control method and device for grid-type converters. Background Technology

[0002] Driven by the dual-carbon development goals, a high proportion of renewable energy is connected to the power system via power electronic converters, reducing the proportion of conventional synchronous generators and resulting in a prominent low-inertia characteristic of the new power system. When facing large load fluctuations, short-circuit faults, and other major disturbances, the new power system exhibits rapid frequency changes and a low minimum instantaneous voltage drop, affecting the power supply quality to frequency-sensitive loads and even easily causing malfunctions of protection devices based on frequency changes. To address this issue, virtual inertia technology for grid-connected converters, represented by virtual synchronous generator control, has emerged. This technology uses grid-connected converter control to simulate the external characteristics of traditional synchronous generators, thereby mitigating the rate of frequency change and controlling the maximum / minimum change values ​​when facing disturbances. Based on the overall reliability of the power system, its operating states typically include three types: normal, alert, and fault. The specific operating characteristics corresponding to each state are as follows:

[0003] 1) Normal state: The system is in normal operation with no faults and no power quality indicators exceeding the limits. The system has a large power flow safety margin and voltage safety margin, strong anti-disturbance capability, and can achieve safe and reliable power supply.

[0004] 2) Alert state: The system is still in power supply state without faults, but the system has safety hazards and poor anti-disturbance ability. Some indicators reflecting power quality exceed the limit or the safety margin is insufficient, such as voltage exceeding the limit, local heavy overload of power flow, N-1 not being met, emergency power supply, etc.

[0005] 3) Fault state: The system fails to work normally. The fault state is a transient process. The operation of the relay protection device to cut off the fault may cause a temporary loss of power to some loads, and then enter the fault recovery stage.

[0006] Traditional grid-type virtual synchronous generator control technology typically designs the grid-type converter to operate with fixed power and virtual inertia parameters. However, different system operating states have varying support requirements for the grid-type converter. Forcing the power electronic grid-type converter to behave like a fixed synchronous machine fails to fully utilize its flexibility and controllability to address power and inertia support issues under multiple operating states, making it difficult to achieve the goals of mitigating the frequency variation rate of new power systems and maintaining system stability. Therefore, how to adaptively adjust the control mode and virtual inertia of the grid-type converter during different operating states to accurately respond to the system's voltage and frequency support requirements is crucial for the system's safety and stability. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a virtual inertia adaptive control method and device for grid-type converters, so as to realize the adaptive virtual inertia adjustment and active and reactive power response support of grid-type converters when the power system is operating randomly in normal state, warning state and fault state, improve the frequency dynamic response characteristics such as frequency change rate and minimum frequency drop value of new power systems, and enhance the stability of systems with a high proportion of new energy.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] According to the virtual inertia adaptive control method for grid-type converters proposed in this invention, the operating state of the power distribution system is determined. If the operating state is a fault state, step A is executed; if the operating state is a warning state, step B is executed.

[0010] Step A is:

[0011] Detect the fault current and adjust the amplitude of the voltage modulation signal and the maximum apparent power of the grid converter based on this current.

[0012] Based on the actual voltage modulation signal amplitude after adaptive adjustment in the fault state and the maximum apparent power of the grid converter, the active power and reactive power reference values ​​of the grid converter are adjusted synchronously.

[0013] Based on the adjusted active and reactive power reference values, the virtual inertia parameters and droop coefficient parameters of the grid converter are adaptively adjusted to achieve optimal active and reactive power response control of the grid converter.

[0014] Step B is:

[0015] Obtain the active power and reactive power reference values ​​of the grid-type converter in the alert state;

[0016] Based on the given reference values ​​of active and reactive power, the virtual inertia parameters and droop coefficient parameters of the grid-type converter are adaptively adjusted to achieve optimal active and reactive power response control of the grid-type converter.

[0017] As a further optimization scheme of the virtual inertia adaptive control method for the network converter described in this invention, step A is as follows:

[0018] Step A: Detect the fault current and adjust the voltage modulation signal amplitude and the maximum apparent power of the grid-type converter based on this current.

[0019]

[0020] in, The actual voltage modulation signal amplitude of the i-th grid-type converter after adaptive adjustment under fault conditions. Let i be the maximum allowable single-phase output current of the i-th grid-type converter. Let be the single-phase equivalent impedance of the i-th grid-type converter. The amplitude of the single-phase voltage modulation signal generated for the control loop of the i-th grid-type converter;

[0021]

[0022] in, This represents the maximum apparent power of the i-th grid-type converter after adaptive adjustment in fault condition. Let be the auxiliary power adjustment coefficient for the i-th grid-type converter. Let be the rated voltage amplitude of the i-th grid-type converter. Let be the maximum apparent power of the i-th grid-type converter under the normal operating state of the power distribution system;

[0023] Based on the actual voltage modulation signal amplitude after adaptive adjustment in the fault state and the maximum apparent power of the grid converter, the active power and reactive power reference values ​​of the grid converter are adjusted synchronously.

[0024]

[0025] in, A reference value is given for the active power of the i-th grid-type converter under fault conditions. A reference value is given for the reactive power of the i-th grid-type converter under fault conditions. Let be the maximum allowable reactive power output of the i-th grid-type converter. Let be the rated voltage amplitude of the i-th grid-type converter. The rated amplitude of the grid connection point voltage. This represents the actual voltage amplitude at the grid connection point. This represents the maximum allowable active power output of the i-th grid-type converter;

[0026] Based on the adjusted active and reactive power reference values, the virtual inertia parameters and droop coefficient parameters of the grid converter are adaptively adjusted to achieve optimal active and reactive power response control of the grid converter.

[0027] As a further optimization scheme of the virtual inertia adaptive control method for the network converter described in this invention, step B is as follows:

[0028] Step B: Obtain the active power reference value of the i-th grid-type converter in the alert state. Reactive power reference value ;in,

[0029] ,

[0030] in, , , , These are the minimum active power, maximum active power, minimum reactive power, and maximum reactive power values ​​allowed to be output by the i-th grid-type converter, respectively.

[0031] Based on the given reference values ​​of active and reactive power, the virtual inertia parameters and droop coefficient parameters of the grid-type converter are adaptively adjusted to achieve optimal active and reactive power response control of the grid-type converter.

[0032] As a further optimization scheme of the virtual inertia adaptive control method for a grid-type converter described in this invention, the virtual inertia parameters of the grid-type converter refer to the state-adaptive virtual inertia time constant of the active-frequency control loop and the state-adaptive virtual inertia time constant of the voltage-reactive power control loop; the droop coefficient parameters refer to the state-adaptive active power droop coefficient and the state-adaptive reactive power droop coefficient.

[0033] The active-frequency control loop state adaptive virtual inertia time constant is:

[0034]

[0035] in, Let [k] be the adaptive virtual inertia time constant of the active power-frequency control loop of the i-th grid-type converter. The superscript [k] indicates the state, where k=1, 2, and 3 correspond to the normal state, the alert state, and the fault state, respectively. Let be the adjustment coefficient of the active-frequency control loop of the i-th grid-type converter. The active power state adaptive setpoint is given for the i-th grid-type converter. Let i be the rated active power of the i-th grid-type converter. The active-frequency control loop state adaptive virtual inertia time constant of the i-th grid-type converter under normal conditions of the power distribution system;

[0036] The state-adaptive virtual inertia time constant of the voltage-reactive power control loop is

[0037]

[0038] in, Let be the state adaptive virtual inertia time constant of the voltage-reactive power control loop of the i-th grid-type converter. Let be the adjustment coefficient of the voltage-reactive power control loop of the i-th grid-type converter. The state-adaptive reactive power setpoint is given for the i-th grid-type converter. Let i be the reactive power rating of the i-th grid-type converter. The voltage-reactive power control loop state adaptive virtual inertia time constant of the i-th grid-type converter under normal conditions of the power distribution system;

[0039] State-adaptive active power droop coefficient:

[0040]

[0041] in, Let be the adaptive droop coefficient of the active-frequency control loop state of the i-th grid-type converter. This represents the adaptive droop coefficient for the active-frequency control loop of the i-th grid-type converter under normal conditions in the power distribution system. Based on the maximum allowable active power droop factor of the rated capacity of the i-th grid-type converter, Let be the active power sensing coefficient of the i-th grid-type converter;

[0042] State-adaptive reactive power droop coefficient:

[0043]

[0044] in, Let be the adaptive droop coefficient of the reactive power-voltage control loop state of the i-th grid-type converter. This represents the adaptive droop coefficient for the reactive power-voltage control loop of the i-th grid-type converter under normal conditions in the power distribution system. Based on the maximum allowable reactive power droop factor of the rated capacity of the i-th grid-type converter, Let be the reactive power sensing coefficient of the i-th grid-type converter.

[0045] An apparatus for a virtual inertia adaptive control method for a grid-type converter includes an operating state judgment module, a reference power generation module, a virtual inertia adaptive adjustment and power tracking control module, and a PWM drive signal generation module; wherein,

[0046] The operation status judgment module is used to determine the current operation status based on the voltage status of the grid connection point PCC: to determine the operation status of the power distribution system, which is either fault state, alarm state, or normal state.

[0047] The reference power generation module is used to detect the fault current when the operating state is faulty, and adjust the voltage modulation signal amplitude and the maximum apparent power of the grid converter according to the current. Based on the actual voltage modulation signal amplitude and the maximum apparent power of the grid converter after adaptive adjustment in the fault state, the active power and reactive power reference values ​​of the grid converter are adjusted synchronously.

[0048] When the operating state is in the alert state, obtain the active power and reactive power reference values ​​of the grid-type converter in the alert state;

[0049] The active and reactive power of the grid-type converter are transferred to the virtual inertial adaptive adjustment and power tracking control module;

[0050] The virtual inertia adaptive adjustment and power tracking control module is used to obtain the adjusted active power and reactive power reference values ​​of each grid converter under the current state, and to adaptively adjust the virtual inertia parameters and droop coefficient parameters of the grid converter, thereby realizing the optimal response control of the active and reactive power of the grid converter.

[0051] The PWM drive signal generation module is used to send a high-level turn-on drive signal or a low-level turn-off signal to the IGBT control terminal in the grid-type converter.

[0052] As a further optimization of the device for the virtual inertia adaptive control method of the grid-type converter described in this invention, the operating state judgment module collects the actual operating voltage of the grid-connected point PCC through a voltage Hall element, calculates the voltage amplitude and compares it with the voltage thresholds corresponding to the normal state, warning state and fault state respectively, judges the current actual operating state, and transmits the judgment result to the reference power generation module.

[0053] As a further optimization of the device for the virtual inertia adaptive control method of the grid-type converter described in this invention, the virtual inertia adaptive adjustment and power tracking control module adaptively adjusts the following: the state adaptive virtual inertia time constant of the active-frequency control loop, the state adaptive virtual inertia time constant of the voltage-reactive power control loop, the state adaptive active power droop coefficient, and the state adaptive reactive power droop coefficient of the grid-type converter.

[0054] As a further optimization of the device for the virtual inertia adaptive control method of the grid-type converter described in this invention, the PWM drive signal generation module generates a square wave signal by combining the voltage modulation signal generated by the virtual inertia adaptive adjustment and power tracking control module with a triangular carrier signal. This square wave signal is used to send a high-level turn-on drive signal or a low-level turn-off signal to the IGBT control terminal in the grid-type converter. Ultimately, this achieves virtual inertia adaptive control of the grid-type converter under different operating states.

[0055] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0056] This invention primarily addresses the issue of grid-connected converters supporting the frequency response of novel power systems with a high proportion of renewable energy under different operating states (normal, alert, and fault). It proposes a virtual inertia adaptive control method, device, and medium for grid-connected converters considering multiple state switching modes (normal, alert, and fault). This enables adaptive virtual inertia adjustment and active / reactive power response support of the grid-connected converters under random system operation in normal, alert, and fault states, improving the frequency dynamic response characteristics of novel power systems, such as the rate of frequency change and minimum frequency drop, thereby enhancing the stability of systems with a high proportion of renewable energy. Attached Figure Description

[0057] Figure 1 This is a basic architecture diagram of a new type of power system.

[0058] Figure 2 This is a grid-connected structure diagram of a single grid-type converter.

[0059] Figure 3 This is a control flowchart of one embodiment.

[0060] Figure 4 This is the local control schematic diagram of a network converter.

[0061] Figure 5 Schematic diagram for generating PWM drive signals.

[0062] Figure 6 This refers to the voltage amplitude at the network converter terminals during the system's transition from normal to fault state when using traditional technology in the implementation case.

[0063] Figure 7 The output power of the grid-type converter under the change from normal state to fault state in the implementation case using traditional technology.

[0064] Figure 8 The frequency of the grid converter is determined by the system's normal state to fault state changes when using traditional technology in the implementation case.

[0065] Figure 9 This is to measure the voltage amplitude at the grid-type converter terminals during the system's transition from normal to alert state when using traditional technology in the implementation case.

[0066] Figure 10 The output power of the grid converter under the system's normal to alert state changes when using traditional technology in the implementation case.

[0067] Figure 11 The frequency of the grid converter is determined by the system's normal state to alert state change when using traditional technology in the implementation case.

[0068] Figure 12The voltage amplitude at the grid converter terminals during the change from normal to fault state when the technology of this invention is used in the implementation case.

[0069] Figure 13 The output power of the grid converter under the change from normal state to fault state when the technology of this invention is used in the implementation case.

[0070] Figure 14 The frequency of the grid converter under the change from normal state to fault state when the technology of this invention is used in the implementation case.

[0071] Figure 15 The voltage amplitude at the grid converter terminals during the change from the normal state to the alert state when the technology of this invention is used in the implementation case.

[0072] Figure 16 The output power of the grid converter under the change from normal state to alert state when the technology of this invention is used in the implementation case.

[0073] Figure 17 The frequency of the grid converter under the change from normal state to alert state when the technology of this invention is used in the implementation case. Detailed Implementation

[0074] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0075] The present invention aims to provide a method, device, and medium for power support and virtual inertia adaptive control of a grid-type converter considering multiple operating states such as normal state, alert state, and fault state. It mainly consists of an operating state judgment module, a reference power generation module, a virtual inertia adaptive adjustment and power tracking control module, and a PWM drive signal generation module. The method includes the following steps:

[0076] like Figure 1 As shown, the new power system includes a high proportion of distributed renewable energy sources such as wind turbines and photovoltaics. These various distributed renewable energy sources typically take the form of... Figure 2 The power electronic interface converter shown is connected to the power grid. Then, the converter control unit controls the output of active and reactive power, achieving flexible power interaction with the grid side. New energy grid-connected systems have advantages such as fast response speed and flexible controllability; however, this also leads to a reduction in the overall system inertia. From the perspective of new power systems, based on the system's inertia response characteristics and the relationship between frequency change rate and power, there are two main ways to mitigate frequency changes: increasing the system's inherent inertia and reducing the disturbance differential power.

[0077] 1. The core idea of ​​the operating status judgment module and the reference power generation module is as follows: Figure 3As shown, the current operating status is determined based on the voltage at the PCC point. Next, based on the system support requirements for the current operating status, the active and reactive power outputs of the grid-connected converter are calculated and generated, and then transmitted to the grid-connected converter control system.

[0078] The relationship between system status, grid connection point voltage, and active and reactive power commands is shown in Table 1. This is the rated voltage at the grid connection point. P is the actual value of the grid connection point voltage. [k] seti A reference value is given for the active power of the i-th grid-type converter, P ni P is the rated reference value of active power for the i-th grid-type converter. maxi and P mini Q represents the maximum and minimum allowable output active power of the i-th grid-type converter, respectively. [k] seti A reference value is given for the reactive power of the i-th grid-type converter, Q. ni Q is the rated reference value of reactive power for the i-th grid-type converter. maxi and Q mini S represents the maximum and minimum allowable reactive power output of the i-th grid-type converter, respectively. maxi The maximum apparent power allowed to be output by the i-th grid-type converter. Let be the rated voltage amplitude of the i-th grid-type converter.

[0079] Table 1. System Operating Status - Grid Connection Point Voltage - Active and Reactive Power Given Reference Value Command Mapping Relationship

[0080]

[0081] (1) Under normal conditions, the system voltage is within a reasonable and stable range. The grid-type converter operates at approximately its rated capacity, and its virtual inertia and droop coefficient are calculated based on the rated capacity. This ensures optimal frequency response and reasonable active and reactive power support within normal load fluctuations.

[0082] (2) Alert state: The system voltage exceeds the normal operating range but has not reached the fault state. Preventive measures need to be taken, prioritizing system safety and reliability. The system should be transitioned to normal operating state as soon as possible through active and reactive power compensation, so as to achieve multi-level coordination, reduce risks, and ensure safe operation. The system will flexibly allocate the controllable grid converter within its maximum and minimum allowable output active and reactive power range to provide flexible active and reactive power support.

[0083] (3) Fault state: When the system voltage reaches the fault state judgment standard, the grid-connected converter needs to inject active and reactive power into the system according to the low voltage ride-through standard. This invention is based on the GB / T 33593-2017 distributed micro-source grid connection standard, which requires that for every 1% voltage drop, the micro-source must provide at least 2% reactive current, resulting in the active and reactive power reference value calculation standard as shown in Table 1. (This invention provides a calculation algorithm for obtaining the active and reactive power reference values ​​of the micro-source from the standard, and its input can also be based on other regional standards, possessing general applicability.)

[0084] 2. The core idea of ​​the virtual inertial adaptive adjustment and power point tracking control module is:

[0085] like Figure 3 As shown, after analysis and state judgment, each grid-type converter obtains the active and reactive power reference commands for the current state. Next, the virtual inertia and droop coefficient parameters of the grid-type converter are adaptively adjusted to change its own power output and frequency response state, coordinating with other grid-type converters to achieve the optimal frequency response for different states. Table 2 shows the set of key parameter variables corresponding to different states. The adaptive control principle of the grid-type converter under different states is explained in detail below.

[0086] Table 2. Set of key parameter variables for different states

[0087]

[0088] The local control principle of the grid-type converter with multi-state adaptive capability is as shown in equations (1) and (2), including the active-frequency control loop (equation (1)) and the reactive-voltage control loop (equation (2)).

[0089] (1)

[0090] (2)

[0091] Among them, H i [k] For the virtual rotational inertia of the network converter, This is the actual angular frequency of the grid-type converter. D is the angular frequency setpoint for the mesh converter. pi [k] This refers to the active power loop droop factor of the grid-type converter. This is the active power setpoint for the grid-type converter. This represents the actual output active power of the grid-type converter. Virtual inertia of the reactive power loop for grid-type converters For virtual excitation of the grid-type converter, This refers to the actual reactive power output of the grid-type converter. The rated reactive power of the grid-type converter, This refers to the reactive power loop droop factor of the grid-type converter. This refers to the rated voltage amplitude of the grid-type converter. Let k represent the actual voltage amplitude of the grid-connected converter, and k be the corresponding system state flag: normal state (k=1), alert state (k=2), and fault state (k=3). Based on the relationship between the rated active and reactive power, actual output active and reactive power capacity, virtual inertia, and droop characteristics of the grid-connected converter, this invention provides specific parameters for different states.

[0092] (1) Under normal conditions (k=1), the main parameters of the active-frequency and reactive-voltage control loops are given based on the rated capacity of the grid-type converter.

[0093] The virtual inertia of the active loop is:

[0094] (3)

[0095] The active power loop droop coefficient is:

[0096] (4)

[0097] Reactive power converted into virtual inertia is:

[0098] (5)

[0099] The reactive power loop droop factor is:

[0100] (6)

[0101] in, The virtual inertial time constant of the active-frequency control loop. These are the minimum and maximum allowed frequencies for the mesh-type converter, respectively. The virtual inertia time constant of the voltage-reactive power control loop. These represent the minimum and maximum allowable voltage amplitudes for the grid-type converter, respectively.

[0102] (2) Alert state (k=2): Based on the active and reactive power reference values ​​given by the upper-level control module for the actual operating conditions, the main parameters of the active-frequency and reactive-voltage control loops are adaptively adjusted.

[0103] The active-frequency control loop state adaptive virtual inertia time constant is:

[0104] (7)

[0105] The state-adaptive virtual inertia time constant of the voltage-reactive power control loop is

[0106] (8)

[0107] State-adaptive active power droop coefficient:

[0108] (9)

[0109] State-adaptive reactive power droop coefficient:

[0110] (10)

[0111] in, Let be the adjustment coefficient of the active-frequency control loop of the i-th grid-type converter. Let be the adjustment coefficient of the voltage-reactive power control loop of the i-th grid-type converter. Based on the maximum allowable active power droop factor of the rated capacity of the i-th grid-type converter, Let be the active power sensing coefficient of the i-th grid-type converter. Based on the maximum allowable reactive power droop factor of the rated capacity of the i-th grid-type converter, Let be the reactive power sensing coefficient of the i-th grid-type converter.

[0112] (3) Fault state (k=3): Compared with the other two states, the fault state requires a significant adjustment of active and reactive power output. At the same time, due to the thermal capacity of power electronic devices, it is necessary to consider limiting the fault state output current of the grid-type converter.

[0113] As shown in equation (11), based on the maximum permissible single-phase output current of the grid-type converter under actual fault conditions... Multiply by the single-phase equivalent impedance of the network converter The amplitude of the single-phase voltage modulation signal generated by the control loop of the multiplicative converter is compared with the product. The minimum of these two values ​​is taken as the actual voltage modulation signal amplitude under fault conditions. The active and reactive power reference values ​​given under different operating conditions of the new power distribution system are adaptively adjusted, as shown in equation (12). First, the maximum apparent power of the grid-type converter is proportionally changed. Then, the actual active and reactive power reference values ​​are corrected according to Table 1. That is, the reactive power is kept at Qseti according to the upper-level instruction, and the active power reference value Pseti will be adjusted according to the adjusted apparent power. Finally, the main parameters of the active-frequency and reactive-voltage control loops are adaptively adjusted according to equations (7)-(10).

[0114] (11)

[0115] (12)

[0116] in, This refers to the maximum permissible single-phase output current of the grid-type converter. The single-phase equivalent impedance of the grid-type converter in fault condition. The single-phase voltage modulation signal generated by the control loop of the grid-type converter. The actual voltage modulation signal amplitude after adaptive adjustment under fault conditions. This represents the maximum apparent power of the grid-type converter after adaptive adjustment under fault conditions. As an auxiliary power adjustment coefficient, This refers to the rated voltage amplitude of the grid-type converter.

[0117] like Figure 3 As shown, the generated virtual inertia parameters and droop coefficient are then transmitted to the active-frequency and reactive-voltage droop control modules, as follows: Figure 4 The traditional virtual synchronous converter control principle is shown, followed by the generation of a voltage modulation signal e. ref It is transmitted to the PWM drive signal generation module.

[0118] 4. PWM drive signal generation module:

[0119] Specific control methods are as follows: Figure 5 As shown, the PWM drive signal generation module receives the output signal from the preceding control stage. In general, there are , will signal Compared with a 10kHz sawtooth wave within the module, when the signal value When the signal value is less than or equal to the sawtooth wave signal value, the PWM drive signal generation module sends a high-level turn-on drive signal to the IGBT control terminal in the grid converter until the signal value is less than or equal to the sawtooth wave signal value. If the value is greater than the sawtooth wave signal value, the PWM drive signal generation module sends a low-level turn-off signal to the IGBT control terminal. This example only uses the existing model sawtooth wave signal frequency of 10kHz as an example, and this frequency value is only used as an example. In actual applications, this frequency is not limited to this value.

[0120] like Figure 6-8 and Figure 12-14As shown, comparing the waveforms of the example without and with the present invention when switching from the normal state to the fault state of the distribution network, it can be seen that without the present invention, the output power of the grid-type converter will oscillate significantly, making it impossible to achieve reasonable active and reactive power injection. The frequency will change drastically, and the minimum frequency drop at the moment of fault occurrence exceeds the maximum allowable fluctuation range on the grid side. After the fault is cleared, the frequency experiences a significant recovery-state impact. With the present invention, active and reactive power injection can be flexibly performed, adjusting the rated active and reactive power output ratio according to the grid-side power support requirements to support the grid-side voltage. Simultaneously, the virtual inertia is adaptively adjusted to obtain the optimal voltage and frequency response characteristics under the current state. The comparison shows that the minimum frequency drop at the time of fault occurrence is significantly reduced, and the maximum frequency peak during the recovery phase after fault clearance is also significantly reduced.

[0121] like Figure 9-11 and Figure 15-17 As shown, comparing the waveforms of the calculation examples without and with the application of the present invention when the distribution network switches from normal state to alert state, it can be seen that without the application of the present invention, the alert state cannot adaptively track the grid-side early warning control and provide active and reactive power support; with the application of the present invention, it can flexibly track the upper-level reference commands, provide flexible active and reactive power support to the grid side, and adaptively adjust the virtual inertia to obtain the optimal voltage and frequency response characteristics under the current state.

[0122] The circuit and grid-type converter example parameters are shown in Table 3;

[0123] Table 3. Circuit and Network Converter Example Parameters

[0124]

[0125] An apparatus for a virtual inertia adaptive control method for a grid-type converter includes an operating state judgment module, a reference power generation module, a virtual inertia adaptive adjustment and power tracking control module, and a PWM drive signal generation module; wherein,

[0126] The operation status determination module is used to determine the current operation status based on the voltage status of the grid connection point PCC.

[0127] The reference power generation module is used to calculate and generate the active and reactive power of the grid-type converter based on the current operating status, and then pass it to the virtual inertial adaptive adjustment and power tracking control module.

[0128] The virtual inertia adaptive adjustment and power tracking control module is used to obtain the active and reactive power of each grid-type converter in the current state, adaptively adjust the virtual inertia and droop coefficient parameters of the grid-type converter, change its own power output and participate in the frequency modulation response state, and coordinate with other converters to achieve the optimal frequency response for different states.

[0129] The PWM drive signal generation module is used to send a high-level turn-on drive signal or a low-level turn-off signal to the IGBT control terminal in the grid-type converter.

[0130] Furthermore, the operation status judgment module collects the actual operating voltage of the grid-connected PCC point through a voltage Hall element, calculates the voltage amplitude and compares it with the voltage thresholds corresponding to the normal state, warning state and fault state, respectively, to determine the current actual operating state, and transmits the judgment result to the reference power generation module.

[0131] Furthermore, the reference power generation module calculates and generates the active and reactive power reference values ​​of the grid converter based on the current operating status result output by the operating status judgment module and the rated active and reactive power values ​​of the grid converter, and transmits them to the virtual inertial adaptive adjustment and power tracking control module.

[0132] Furthermore, the virtual inertia adaptive adjustment and power point tracking control module uses the active and reactive power reference values ​​and initial virtual inertia values ​​of the grid-connected converter calculated by the reference power generation module. The adaptive adjustments are made to: the state-adaptive virtual inertia time constant of the active-frequency control loop, the state-adaptive virtual inertia time constant of the voltage-reactive power control loop, the state-adaptive active power droop coefficient, and the state-adaptive reactive power droop coefficient of the grid-connected converter. Then, the adjusted parameters are passed to the active-frequency and reactive-voltage control loops of the grid-connected converter. This changes the active and reactive power output and frequency regulation response state of each grid-connected converter in its current state, coordinating with other converters to achieve optimal frequency response for different states.

[0133] Furthermore, the PWM drive signal generation module generates a square wave signal from the voltage modulation signal and triangular carrier signal generated by the virtual inertia adaptive adjustment and power tracking control module. This square wave signal is used to send a high-level turn-on drive signal or a low-level turn-off signal to the IGBT control terminal in the grid-type converter. Ultimately, this achieves virtual inertia adaptive control under different operating states of the grid-type converter.

[0134] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0135] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0136] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0137] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0138] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0139] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A grid-forming converter virtual inertia adaptive control method, characterized in that, Determine the operating status of the power distribution system. If the operating status is a fault state, proceed to step A; if the operating status is a warning state, proceed to step B. Step A is: Detect the fault current and adjust the amplitude of the voltage modulation signal and the maximum apparent power of the grid converter based on this current. Based on the actual voltage modulation signal amplitude after adaptive adjustment in the fault state and the maximum apparent power of the grid converter, the active power and reactive power reference values ​​of the grid converter are adjusted synchronously. Based on the adjusted active and reactive power reference values, the virtual inertia parameters and droop coefficient parameters of the grid converter are adaptively adjusted to achieve optimal active and reactive power response control of the grid converter. Step B is: Obtain the active power and reactive power reference values ​​of the grid-type converter in the alert state; Based on the given reference values ​​of active power and reactive power, the virtual inertia parameters and droop coefficient parameters of the grid-type converter are adaptively adjusted to achieve optimal active and reactive response control of the grid-type converter. Step A is as follows: Step A: Detect the fault current and adjust the voltage modulation signal amplitude and the maximum apparent power of the grid-type converter based on this current. ； wherein, is the actual voltage modulation signal amplitude of the ith grid-forming converter after adaptive adjustment in the fault state, is the maximum allowable output current of the ith grid-forming converter per phase, is the equivalent impedance of the ith grid-forming converter per phase, is the voltage modulation signal amplitude generated by the control loop of the ith grid-forming converter per phase; ； in, This represents the maximum apparent power of the i-th grid-type converter after adaptive adjustment in fault condition. Let be the auxiliary power adjustment coefficient for the i-th grid-type converter. Let be the rated voltage amplitude of the i-th grid-type converter. Let be the maximum apparent power of the i-th grid-type converter under the normal operating state of the power distribution system; Based on the actual voltage modulation signal amplitude after adaptive adjustment in the fault state and the maximum apparent power of the grid converter, the active power and reactive power reference values ​​of the grid converter are adjusted synchronously. ； in, A reference value is given for the active power of the i-th grid-type converter under fault conditions. A reference value is given for the reactive power of the i-th grid-type converter under fault conditions. Let be the maximum allowable reactive power output of the i-th grid-type converter. Let be the rated voltage amplitude of the i-th grid-type converter. The rated amplitude of the grid connection point voltage. This represents the actual voltage amplitude at the grid connection point. This represents the maximum allowable active power output of the i-th grid-type converter; Based on the adjusted active and reactive power reference values, the virtual inertia parameters and droop coefficient parameters of the grid converter are adaptively adjusted to achieve optimal active and reactive power response control of the grid converter.

2. The virtual inertia adaptive control method for a network converter according to claim 1, characterized in that, Step B is as follows: Step B: Obtain the active power reference value of the i-th grid-type converter in the alert state. Reactive power reference value ;in, ， ； in, , , , These are the minimum active power, maximum active power, minimum reactive power, and maximum reactive power values ​​allowed to be output by the i-th grid-type converter, respectively. Based on the given reference values ​​of active and reactive power, the virtual inertia parameters and droop coefficient parameters of the grid-type converter are adaptively adjusted to achieve optimal active and reactive power response control of the grid-type converter.

3. The virtual inertia adaptive control method for a network converter according to claim 1, characterized in that, The virtual inertia parameters of the grid-type converter refer to the state-adaptive virtual inertia time constant of the active-frequency control loop and the state-adaptive virtual inertia time constant of the voltage-reactive power control loop; the droop coefficient parameters refer to the state-adaptive active power droop coefficient and the state-adaptive reactive power droop coefficient. The active-frequency control loop state adaptive virtual inertia time constant is: ； in, Let [k] be the adaptive virtual inertia time constant of the active power-frequency control loop of the i-th grid-type converter. The superscript [k] indicates the state, where k=1, 2, and 3 correspond to the normal state, the alert state, and the fault state, respectively. Let be the adjustment coefficient of the active-frequency control loop of the i-th grid-type converter. The active power state adaptive setpoint is given for the i-th grid-type converter. Let i be the rated active power of the i-th grid-type converter. The active-frequency control loop state adaptive virtual inertia time constant of the i-th grid-type converter under normal conditions of the power distribution system; The state-adaptive virtual inertia time constant of the voltage-reactive power control loop is ； in, Let be the state adaptive virtual inertia time constant of the voltage-reactive power control loop of the i-th grid-type converter. Let be the adjustment coefficient of the voltage-reactive power control loop of the i-th grid-type converter. The state-adaptive reactive power setpoint is given for the i-th grid-type converter. Let i be the reactive power rating of the i-th grid-type converter. The voltage-reactive power control loop state adaptive virtual inertia time constant of the i-th grid-type converter under normal conditions of the power distribution system; State-adaptive active power droop coefficient: ； in, Let be the adaptive droop coefficient of the active-frequency control loop state of the i-th grid-type converter. This represents the adaptive droop coefficient for the active-frequency control loop of the i-th grid-type converter under normal conditions in the power distribution system. Based on the maximum allowable active power droop factor of the rated capacity of the i-th grid-type converter, Let be the active power sensing coefficient of the i-th grid-type converter; State-adaptive reactive power droop coefficient: ； in, Let be the adaptive droop coefficient of the reactive power-voltage control loop state of the i-th grid-type converter. This represents the adaptive droop coefficient for the reactive power-voltage control loop of the i-th grid-type converter under normal conditions in the power distribution system. Based on the maximum allowable reactive power droop factor of the rated capacity of the i-th grid-type converter, Let be the reactive power sensing coefficient of the i-th grid-type converter.

4. An apparatus for a virtual inertia adaptive control method for a network converter, characterized in that, The virtual inertia adaptive control method for a grid-type converter according to any one of claims 1 to 3 includes an operating state judgment module, a reference power generation module, a virtual inertia adaptive adjustment and power tracking control module, and a PWM drive signal generation module; wherein... The operation status judgment module is used to determine the current operation status based on the voltage status of the grid connection point PCC: to determine the operation status of the power distribution system, which is either fault state, alarm state, or normal state. The reference power generation module is used to detect the fault current when the operating state is faulty, and adjust the voltage modulation signal amplitude and the maximum apparent power of the grid converter according to the current. Based on the actual voltage modulation signal amplitude and the maximum apparent power of the grid converter after adaptive adjustment in the fault state, the active power and reactive power reference values ​​of the grid converter are adjusted synchronously. When the operating state is in the alert state, obtain the active power and reactive power reference values ​​of the grid-type converter in the alert state; The active and reactive power of the grid-type converter are transferred to the virtual inertial adaptive adjustment and power tracking control module; The virtual inertia adaptive adjustment and power tracking control module is used to obtain the adjusted active power and reactive power reference values ​​of each grid converter under the current state, and to adaptively adjust the virtual inertia parameters and droop coefficient parameters of the grid converter, thereby realizing the optimal response control of the active and reactive power of the grid converter. The PWM drive signal generation module is used to send a high-level turn-on drive signal or a low-level turn-off signal to the IGBT control terminal in the grid-type converter.

5. The apparatus for a virtual inertia adaptive control method for a network converter according to claim 4, characterized in that, The operation status judgment module collects the actual operating voltage of the grid-connected PCC point through a voltage Hall element, calculates the voltage amplitude and compares it with the voltage thresholds corresponding to the normal state, warning state and fault state, respectively, to determine the current actual operating state, and transmits the judgment result to the reference power generation module.

6. The apparatus for a virtual inertia adaptive control method for a network converter according to claim 4, characterized in that, In the virtual inertia adaptive adjustment and power tracking control module, the adaptive adjustments are made to: the state adaptive virtual inertia time constant of the active-frequency control loop, the state adaptive virtual inertia time constant of the voltage-reactive power control loop, the state adaptive active power droop coefficient, and the state adaptive reactive power droop coefficient of the grid-type converter.

7. The apparatus for a virtual inertia adaptive control method for a network converter according to claim 4, characterized in that, The PWM drive signal generation module generates a square wave signal by combining the voltage modulation signal and triangular carrier signal generated by the virtual inertia adaptive adjustment and power tracking control module. This square wave signal is used to send a high-level turn-on drive signal or a low-level turn-off signal to the IGBT control terminal in the grid-type converter. Ultimately, this enables virtual inertia adaptive control of the grid-type converter under different operating states.

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