Inertia cooperative control method for integrated optical storage AC / DC hybrid micro-grid system

Abstract

An inertia cooperative control method of an integrated optical storage alternating current and direct current hybrid micro-grid comprises the steps that firstly, according to static and dynamic power capacities of energy storage units in direct current sub-grids and allowed direct current voltage deviation, sub-grid equivalent virtual resistance and virtual capacitance are calculated; secondly, RC + R type parallel virtual impedance parameters are distributed according to the power proportion of each energy storage unit, and multi-energy-storage cooperative response power disturbance according to the capacity is achieved; then, a phase angle is generated based on the mapping relation between direct-current side voltage and frequency, an alternating-current voltage amplitude instruction is determined in combination with reactive power droop control and feeder impedance voltage drop compensation, and a dq-axis voltage instruction is generated through virtual impedance compensation; normalized three-phase modulation waves are obtained through voltage-current double closed-loop control and dq / abc coordinate transformation, and six paths of PWM signals are generated to drive an interconnection converter after the normalized three-phase modulation waves are compared with triangular carrier waves. The method does not need to depend on external communication, has the capabilities of autonomous inertia support, voltage and frequency coordinated regulation and reasonable multi-source power distribution, and improves the stability and dynamic response performance of the system under island operation.

Description

Technical Field

[0001] This invention relates to the field of microgrid control technology, specifically to an inertia-coordinated control method for an AC / DC hybrid microgrid integrating photovoltaic and energy storage. It is particularly suitable for scenarios where multiple DC subgrids are connected in parallel to the same AC subgrid through interconnecting converters. The aim is to solve the problem of system voltage and frequency stability when the load changes rapidly, and to achieve the proportional distribution of output active and reactive power. Background Technology

[0002] With the large-scale integration of renewable energy, hybrid AC / DC microgrids have become an important form of future power distribution systems due to their ability to efficiently accommodate DC power sources such as photovoltaics and diverse AC / DC loads. In a typical architecture, multiple independent DC subgrids, usually composed of photovoltaics, energy storage, and DC loads, are connected in parallel to the same AC bus through their respective interconnecting converters, forming a complex network with multi-source collaboration and bidirectional energy flow.

[0003] As a core hub connecting the AC and DC subgrids, the ILC not only undertakes power dispatching functions but also needs to provide effective inertia and damping support under dynamic disturbances. Although existing adaptive droop control and virtual synchronous generator strategies can improve static power balance and steady-state voltage / frequency stability, under disturbances such as rapid power changes, due to unreasonable inertia equivalence, some energy storage units responsible for stabilization may still experience short-term overload, leading to momentary exceedances of DC voltage and AC frequency limits.

[0004] The aforementioned problems limit the dynamic support capability of existing solutions when dealing with frequent and large power fluctuations under the high proportion of renewable energy access. Some energy storage units may exceed the limits of DC voltage or AC frequency due to instantaneous overload, which restricts the overall dynamic and static stability of the system. Summary of the Invention

[0005] To overcome the above-mentioned shortcomings of the prior art, this invention proposes an inertia-coordinated control method for an integrated photovoltaic-storage AC / DC hybrid microgrid, aiming to improve the frequency and voltage stability of the microgrid under dynamic disturbances.

[0006] The core of this invention lies in constructing an equivalent virtual resistance-capacitance model of the DC subgrid and, in conjunction with the static / dynamic power capacity allocation of the energy storage units, designing an RC+R parallel virtual impedance droop control strategy to achieve power fluctuation sharing among the energy storage units according to their capacity. Simultaneously, the interconnecting converter adopts a grid-based control, integrating phase generation based on DC voltage-frequency mapping, reactive power-voltage droop regulation, dq-axis impedance voltage drop compensation, and AC voltage and current dual closed-loop tracking control, forming a complete inertia response and DC voltage and AC frequency support mechanism. The entire system consists of multiple independent DC subgrids containing photovoltaics and loads connected in parallel to the same AC bus through their respective three-phase full-bridge interconnecting converters, realizing multi-source collaboration, inertia sharing, and autonomous stable operation in an AC / DC hybrid microgrid.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides an inertia-coordinated control method for an AC / DC hybrid microgrid integrating photovoltaic and energy storage, having the following circuit topology: comprising at least two independent DC subgrids, each DC subgrid consisting of photovoltaic units, energy storage units, and DC loads, with the energy storage units regulating voltage and power through their respective DC / DC converters; each DC subgrid is connected to an independent interconnecting converter, each interconnecting converter consisting of a three-phase full-bridge inverter circuit, used to convert the DC power of the corresponding DC subgrid into AC power; the AC output terminals of all interconnecting converters are connected in parallel to the common connection point of the same AC subgrid after passing through their respective LC filter networks and line impedances, and supply power to the AC loads, thus forming an AC / DC hybrid microgrid system in which multiple DC subgrids are connected in parallel to the same AC subgrid through their respective interconnecting converters; Includes the following steps: S1. Calculate the equivalent virtual resistance of the DC subgrid based on the total static power capacity of all energy storage devices in the DC subgrid and the maximum allowable deviation of DC voltage; calculate the equivalent virtual capacitance of the DC subgrid based on the total dynamic power capacity of all energy storage devices in the DC subgrid and the maximum allowable rate of change of DC voltage deviation per unit. S2. Calculate the AC virtual impedance based on the dynamic power capacity of the DC subnet and the impedance of the feeder between the AC output side of the interconnected converter and the PCC point according to the proportional relationship.

[0008] S3. Each energy storage unit in the DC subgrid adopts RC+R parallel virtual impedance droop control, including a DC virtual impedance calculation module, a reference voltage calculation module, and a DC voltage tracking control module.

[0009] The S3-1 DC virtual impedance calculation module calculates the parallel virtual resistance, series virtual capacitance, and series virtual resistance of the energy storage unit based on the total static power and total dynamic power of the DC subnet, the static power and dynamic power of the energy storage converter unit under it, as well as the equivalent virtual resistance, equivalent virtual capacitance, and corresponding time constant of the DC subnet. The S3-2 reference voltage calculation module calculates the reference voltage based on the rated voltage of the DC subgrid, the output current of the energy storage units in the DC subgrid, and their corresponding virtual resistance and capacitance. The S3-3 DC voltage tracking control module obtains the duty cycle of the switching transistor based on the reference voltage of the energy storage unit in the DC subgrid, the input battery voltage, and the output current, so that the output voltage changes according to the reference voltage command value under the control of the switch. S4. The interconnected converters connected to each DC subnetwork adopt a network-based control strategy, including a command angle calculation module, a voltage amplitude calculation module, a virtual impedance control module, and an AC voltage tracking control module; The S4-1 command angle calculation module calculates the AC side reference frequency command based on the DC side voltage and mapping parameters of the interconnected converters connected to the DC subnet, and then obtains the phase angle from the frequency through an integrator. The S4-2 command voltage amplitude calculation module calculates the voltage amplitude reference value based on the reactive power and droop factor of the AC output of the interconnected converter connected to the DC subnet; it calculates the impedance voltage drop compensation amount based on the AC output three-phase current, AC feeder resistance and inductance and virtual impedance; and then superimposes the voltage drop compensation amount and the voltage amplitude reference value to obtain the AC voltage amplitude command of the interconnected converter. The S4-3 virtual impedance control module calculates the d / q axis command of the input AC voltage tracking module based on the AC voltage amplitude command of the interconnected converter connected to the DC subnet and after virtual impedance compensation. The S4-4 AC voltage tracking control module calculates the d / q axis components of the modulated wave voltage based on the d / q axis commands of the voltage of the interconnected converter connected to the DC subnet, the actual three-phase output voltage, and the d / q axis components of the output current, and makes the d / q axis components of the actual interconnected converter output voltage change according to the corresponding voltage commands. S5 generates six PWM signals for AC ILC based on the modulation wave voltage.

[0010] Preferably, the equivalent virtual resistance of the i-th DC subnet calculated in step S1 is... The equivalent virtual capacitance of the i-th DC subnet Specifically: (1) In the formula Let be the total static power capacity of all energy storage devices in the i-th DC subgrid. Let be the rated DC voltage of the i-th DC subnet; Let be the actual DC voltage of the i-th DC subnet. For the i-th DC voltage deviation, This is the maximum permissible deviation of the DC voltage. The dynamic power total capacity of all energy storage devices in the i-th DC subgrid; The maximum per-unit rate of change of DC voltage deviation (per-unit rate of change of voltage deviation for all DC subgrids) The maximum permissible rate of change is equal.

[0011] Preferably, step S2 calculates the virtual impedance of the i-th AC subnet. and The specific proportional relationship is as follows: (2) In the formula Let be the resistance of the feeder between PCC points of the i-th AC subnet. Let be the inductance of the feeder between points PCC of the i-th AC subnet.

[0012] Preferably, step S3-1 calculates the parallel virtual resistance of the j-th energy storage unit in the i-th DC subgrid. Series virtual capacitor and series virtual resistance Specifically: (3) In the formula and Let be the static power and dynamic power of the i-th DC subgrid energy storage converter unit j, respectively. is the time constant.

[0013] Preferably, the reference voltage calculated in step S3-2 Specifically: (4) In the formula Let J be the output current of the j-th energy storage unit in the i-th DC subgrid. for Representation in the frequency domain; for Representation in the frequency domain; for Representation in the frequency domain.

[0014] Preferably, the DC voltage tracking control in step S3-3 can employ a dual closed-loop control of DC voltage and current, with the duty cycle d of the switching transistor being... ij The calculation method is as follows: (5) In the formula Let be the input battery voltage of the j-th energy storage converter in the i-th DC subgrid. The duty cycle of the switching transistor. This is the filter inductor current; Inner current loop reference value; , These are the proportional coefficient and integral coefficient of the outer loop of the DC voltage, respectively; , These are the proportional coefficient and integral coefficient of the inner loop of the DC current, respectively.

[0015] Preferably, the AC side reference frequency command in step S4-1 Phase angle obtained with integrator The calculation is as follows: (6) In the formula The mapping parameter between the DC subgrid output voltage and the AC frequency; mod(x,2) ) for x pairs 2 Take the remainder.

[0016] Preferably, the voltage amplitude reference value of the interconnect converter in step S4-2 Specifically: (7) In the formula This refers to the rated voltage amplitude at the AC-side subgrid interconnect converter. To output reactive power in AC mode, This is the droop coefficient; Impedance drop compensation of interconnect converter , The calculation method is as follows: First, output the three-phase AC current. , , Through the following Transformation matrix Converted to d-axis and q-axis components of AC output three-phase current , (8) Then through , Virtual impedance , and the actual impedance of the line , calculate , : (9) AC voltage amplitude command The calculation method is as follows: (10) Wherein, LPF(x) is used to perform low-pass filtering on x.

[0017] Preferably, step S4-3 refers to the d-axis and q-axis commands of the input AC voltage tracking module. and Specifically: (11) The AC voltage tracking control of the interconnect converter i described in step S4-4, and the output of the modulated wave voltage's d-axis and q-axis components, can employ AC voltage and current dual closed-loop control, specifically as follows: The output quantity is obtained from the AC voltage loop equation. , (12) In the formula and Output voltage for interconnect converter i , , The d-axis and q-axis components transformed by formula (8) and These are the d-axis and q-axis command values ​​for the inner current loop of the interconnect converter i, respectively. For the AC filter capacitor of interconnect converter i, and These are the proportional and integral coefficients of the AC voltage outer loop of interconnect converter i, respectively. The AC current closed-loop control is specifically as follows: (13) In the formula and These represent the d-axis and q-axis components of the modulated wave voltage of the interconnect converter i, respectively. For the AC filter inductor of the interconnect converter i, and These are the proportional and integral coefficients of the current inner loop of the interconnect converter i, respectively.

[0018] Preferably, step S5, generating the AC-modulated pulse signal, specifically involves: First , The modulation voltage of the interconnect converter is obtained by the dq to abc transformation. , , : (14) Then, the three-phase modulated wave voltages are divided by the voltages of the corresponding DC subgrids. Half of the signal is normalized to obtain the modulated signal. , , : (15) Finally, a triangular carrier signal with frequency fc is generated. Modulation signal , , and Compare and generate six PWM pulse signals for the upper bridge arm With the lower bridge arm : (16) In a second aspect, the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a computer, implements the inertia coordinated control method of the integrated optical-storage AC / DC hybrid microgrid interconnection converter described in the first aspect.

[0019] This invention addresses hybrid microgrid architectures comprising multiple independent DC subgrids and a shared AC subgrid. It quantifies the inertia characteristics of each DC subgrid by constructing equivalent virtual resistance and virtual capacitance models, and allocates parallel RC+R type virtual impedance parameters based on the static and dynamic power capacities of each energy storage unit. This enables coordinated power disturbance response among energy storage units according to their capabilities. Each DC subgrid is connected to a common AC bus via an independent interconnect converter employing a network-based control strategy. This includes: firstly, generating a phase angle based on the DC-side voltage-frequency mapping relationship; secondly, calculating the AC voltage amplitude command by combining reactive power droop and feeder impedance voltage drop compensation; thirdly, generating a dq-axis voltage command through virtual impedance compensation; and finally, generating a normalized modulation wave and comparing it with a triangular carrier wave through AC voltage-current dual closed-loop control and dq / abc transformation, outputting a PWM drive signal to achieve high-precision voltage tracking. This invention does not rely on external communication and possesses autonomous inertia support, voltage-frequency coordinated adjustment, and multi-source power allocation capabilities, significantly improving the system's stability and dynamic response performance under islanded or weak grid operation.

[0020] The advantages of this invention are as follows: First, by introducing a modeling method based on equivalent virtual resistance and virtual capacitance of energy storage static and dynamic power capacity, the quantitative characterization and flexible adjustment of DC subgrid inertia are realized, effectively suppressing DC voltage surges and improving the system's anti-disturbance capability. Second, by adopting an RC+R parallel virtual impedance droop control strategy based on dynamic power capacity allocation, the power of each energy storage unit is accurately and coordinately distributed under a unified voltage reference, avoiding overload or uneven response. Third, the interconnect converter adopts a grid-type control architecture, integrating voltage-frequency mapping, reactive power-voltage droop, feeder impedance voltage drop compensation, and dq-axis dual closed-loop tracking, which not only enhances the voltage support capability and frequency inertia response of the AC side, but also improves the collaborative stability under multi-terminal interconnection. Finally, the overall topology is modular and scalable, suitable for hybrid microgrid scenarios containing photovoltaic, energy storage, and AC / DC loads, and has both autonomous operation capability and plug-and-play characteristics, significantly improving the system's reliability and dynamic performance under islanded or weak grid conditions. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application 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 embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 A flowchart illustrating the steps of an inertia collaborative control method for an integrated photovoltaic-storage AC / DC hybrid microgrid interconnection converter provided in an embodiment of the present invention; Figure 2 The main circuit diagram of an inertia cooperative control method for an integrated photovoltaic-storage AC / DC hybrid microgrid interconnection converter provided in an embodiment of the present invention; Figure 3 Block diagram of DC-side RC+R droop control for the invention; Figure 4 Block diagram of AC side voltage amplitude command value control for the invention; Figure 5 A block diagram of the AC side-mounted mesh control system for the invention; Figure 6 This is a simulation waveform diagram of the active power output of the DC subgrid in an embodiment of the present invention.

[0023] Figure 7 The image shows a simulated waveform of the reactive power output of the AC subnet in an embodiment of the present invention.

[0024] Figure 8 This is a simulation waveform of the DC subgrid output voltage in an embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] Example 1

[0027] Reference Figure 1 This embodiment provides an inertia coordinated control method for an integrated photovoltaic-storage AC / DC hybrid microgrid, characterized by the following steps in its implementation: A method for coordinated inertia control of an integrated photovoltaic-storage AC / DC hybrid microgrid includes the following steps: S1. Based on the total static power capacity of all energy storage devices in the i-th DC subgrid. Maximum permissible deviation of DC voltage Calculate the equivalent virtual resistance of the DC subnet. Based on the total dynamic power capacity of all energy storage devices in the i-th DC subgrid. DC voltage deviation per unit value (by Rate of change (per unit) Maximum allowed value (All DC subnets) (If the maximum allowable rate of change is equal), calculate the equivalent virtual capacitance of the DC subnet. : (1) In the formula Let be the rated DC voltage of the i-th DC subnet; This represents the actual DC voltage of the i-th DC subnet. This represents the DC voltage offset of the i-th DC subnet. S2. Assume there are N DC subnets, and the dynamic power capacity of the i-th DC subnet is: The resistance of the feeder between the AC output side of the interconnect converter and the PCC point is... Inductance is Calculate the virtual impedance based on the following proportional relationship. and : (2) S3. Assume that the i-th DC subgrid contains j energy storage units, and each energy storage unit adopts RC+R parallel virtual impedance droop control, including a DC virtual impedance calculation module, a reference voltage calculation module, and a DC voltage tracking control module.

[0028] The S3-1 DC virtual impedance calculation module calculates the impedance based on the total static power of the i-th DC subnet. Total dynamic power The static power of energy storage converter unit j Dynamic power and the equivalent resistance of the i-th DC subnet. and equivalent capacitance time constant Calculate the parallel virtual resistance of energy storage unit j Series virtual capacitor and series virtual resistance .

[0029] (3)

[0030] S3-2 Reference Voltage Calculation Module, based on the rated voltage of the i-th DC subgrid. The output current of the j-th energy storage unit in the i-th DC subgrid as well as , and Calculate the reference voltage ; The S3-3 DC voltage tracking control module uses the reference voltage of the j-th energy storage unit in the i-th DC subgrid as a reference. Input side battery voltage and output current Obtain the duty cycle d of the switching transistor. ij To make the output voltage under switch control By instruction value change; S4. The interconnected converters connected to each DC subnetwork adopt a network-based control strategy, including a command angle calculation module, a voltage amplitude calculation module, a virtual impedance control module, and an AC voltage tracking control module; The S4-1 instruction angle calculation module calculates the angle based on the DC-side voltage of the interconnected converter connected to the i-th DC subnet. and mapping parameters Calculate AC side reference frequency command Then by The phase angle is obtained through an integrator. : (4) In the formula The mapping parameter between the DC subgrid output voltage and the AC frequency; mod(x,2) ) for x pairs 2 Take the remainder; The S4-2 command voltage amplitude calculation module calculates the reactive power output of the interconnected converter connected to the i-th DC subnet based on the voltage amplitude. and droop coefficient Calculate the voltage amplitude reference value Based on the AC output three-phase current d-axis and q-axis components after dq transformation , AC feeder resistance and inductor Virtual impedance and Calculate the impedance voltage drop compensation amount , ; to compensate for pressure drop , and voltage amplitude reference value The AC voltage amplitude command of the interconnect converter is obtained by superposition. ; The S4-3 virtual impedance control module controls the AC voltage amplitude according to the command of the interconnected converter connected to the i-th DC subnet. After virtual impedance compensation, the d-axis and q-axis commands of the input AC voltage tracking module are obtained. and ; The S4-4 AC voltage tracking control module, based on the voltage command of the interconnected converter connected to the i-th DC subnet, and Actual three-phase output voltage The d-axis and q-axis components of the output current , AC voltage tracking control enables the d-axis and q-axis components of the output voltage of the actual interconnect converter to be controlled. , According to voltage command and change; S5 Based on the modulation wave voltage , This generates six PWM signals for the AC ILC.

[0031] Step S3-2 Calculation of reference voltage Specifically: (5) for Representation in the frequency domain; for Representation in the frequency domain; for Representation in the frequency domain.

[0032] If the converter connected to the energy storage unit is a Boost converter, the DC voltage tracking control in step S3-3 can adopt DC voltage and current dual closed-loop control, and the duty cycle d of its switching transistor can be set accordingly. ij The calculation method is as follows: (6) In the formula, This is the filter inductor current; This is the inner loop reference value of the current of the j-th energy storage converter in the i-th DC subgrid; , These are the proportional coefficient and integral coefficient of the outer loop of the DC voltage, respectively; , These are the proportional coefficient and integral coefficient of the inner loop of the DC current, respectively; The voltage amplitude reference value of the interconnect converter mentioned in step S4-2 The calculation method is as follows: (7) In the formula The rated voltage amplitude at the AC side sub-network interconnection converter Impedance drop compensation of interconnect converter , The calculation method is as follows: First , , Through the following Transformation matrix AC output current , , Converted to d-axis and q-axis components , (8) Then through , Virtual impedance , and the actual impedance of the line , calculate , : (9) AC voltage amplitude command The calculation method is as follows: (10) Wherein, LPF(x) is used to perform low-pass filtering on x.

[0033] Step S4-3 refers to inputting the d-axis and q-axis commands of the AC voltage tracking module. and Specifically: (11) The AC voltage tracking control of the interconnect converter i described in step S4-4 can be achieved using AC voltage and current dual closed-loop control, specifically as follows: The output quantity is obtained from the AC voltage loop equation. , (12) In the formula and For the d-axis and q-axis components of the output voltage of the interconnect converter i, and These are the d-axis and q-axis command values ​​for the inner current loop of the interconnect converter i, respectively. For the AC filter capacitor of interconnect converter i, and These are the proportional and integral coefficients of the AC voltage outer loop of interconnect converter i, respectively. , , Converted to formula (8) , ; The AC current closed-loop control is specifically as follows: (13) In the formula and These represent the d-axis and q-axis components of the modulated wave voltage of the interconnect converter i, respectively. For the AC filter inductor of interconnect converter i, and These are the proportional and integral coefficients of the inner current loop of the interconnect converter i, respectively; Step S5, generating the AC-modulated pulse signal, specifically involves: First , The modulation voltage of the interconnect converter is obtained by the dq to abc transformation. , , : (14) Then, the three-phase modulated wave voltages are divided by the voltages of the corresponding DC subgrids. Half of the signal is normalized to obtain the modulated signal. , , : (15) Finally, a triangular carrier signal with frequency fc is generated. Modulation signal , , and Compare and generate six PWM pulse signals for the upper bridge arm With the lower bridge arm : (16) Example 2 refer to Figure 2 This invention provides a circuit topology for an inertia-coordinated control method of an AC / DC hybrid microgrid integrating photovoltaic and energy storage. It includes at least two independent DC subgrids, each consisting of a photovoltaic unit, an energy storage unit, and a DC load, with voltage and power regulation achieved through their respective DC / DC converters. Each DC subgrid is connected to an independent interconnecting converter (ILC), each ILC consisting of a three-phase full-bridge inverter circuit, used to convert the DC power of the corresponding DC subgrid into AC power. The AC output terminals of all ILCs are filtered by their respective LC filter networks and line impedance, and then connected in parallel to the common junction point of the same AC subgrid to supply power to the AC load. This constitutes an AC / DC hybrid microgrid system in which multiple DC subgrids are connected in parallel to the same AC subgrid through their respective ILCs.

[0034] Implementing the above embodiments will have the following effects: Simulations of the inertia-coordinated control method for AC / DC hybrid microgrid systems can be performed using simulation tools such as Matlab / Simulink. A converter simulation model is built in Matlab / Simulink to verify the inertia-coordinated control method for the AC / DC hybrid microgrid involved in this application.

[0035] The relevant parameter configurations for the control circuit of the AC / DC hybrid microgrid interconnection converter are as follows: The coefficients of the integrated control method are respectively the maximum allowable fluctuation of the DC side voltage. The maximum allowable value of the maximum permissible rate of change of DC voltage Mapping coefficients =0.53, the equivalent resistance of DC subnet 1 =1.08 Equivalent capacitance =0.062488F and series resistor =0.4 Equivalent resistance of DC subnet 2 =2.16 Equivalent capacitance =0.12498F and series resistor =0.2 The actual line impedance of AC subnet 1 =0 , =50 F, virtual impedance =0.1 , =95mF, actual line impedance of AC subnet 2 =0 , =50 Virtual impedance =0.05 , =45mF.

[0036] Figure 6 The figure shows the simulated output power waveform of the DC subnet. As shown, a sudden load change occurs on the DC side 1 second after the simulation begins. Immediately after the change, the dynamic and static active power of the system are distributed in a 2:1 power ratio. Three seconds later, a sudden load change occurs on the AC side, and the dynamic and static active power of the system are distributed in a 2:1 power ratio.

[0037] Figure 7 The simulation waveform of reactive power output from the AC subnet is shown in the figure. As shown in the figure, a sudden change in DC load occurs 1 second after the simulation starts, and reactive power is distributed according to a 2:1 power ratio; after 3 seconds, a sudden change in AC load occurs, and the system reactive power is distributed according to a 2:1 power ratio.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that the elements inherent in a process, method, article, or apparatus that includes a list of elements are included. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Additionally, portions of the technical solutions provided in the embodiments of this application that are consistent with the implementation principles of corresponding technical solutions in the prior art have not been described in detail to avoid excessive elaboration.

[0039] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An inertia collaborative control method for an integrated optical storage AC-DC hybrid microgrid, characterized in that, The application relates to a hybrid AC / DC micro-grid system, which has the following circuit topology: at least two independent DC sub-networks, each of which is composed of a photovoltaic unit, an energy storage unit and a DC load, and the energy storage unit is regulated in voltage and power through a respective DC / DC converter; each DC sub-network is connected to an independent interconnection converter, and each interconnection converter is composed of a three-phase full-bridge inverter circuit and is used for converting DC power of the corresponding DC sub-network into AC power; AC outputs of all the interconnection converters are connected in parallel to a common connection point of the same AC sub-network through respective LC filter networks and line impedances and supply power to AC loads, so that the hybrid AC / DC micro-grid system is formed. The application comprises the following steps: S1. According to the total static power capacity of all the energy storage devices of the DC sub-network and the maximum allowed deviation of the DC voltage, the equivalent virtual resistance of the DC sub-network is calculated; according to the total dynamic power capacity of all the energy storage devices of the DC sub-network and the maximum allowed value of the standard unit change rate of the DC voltage deviation, the equivalent virtual capacitance of the DC sub-network is calculated; S2. According to the dynamic power capacity of the DC sub-network and the impedance of the feeder between the AC output side of the interconnection converter connected to the DC sub-network and the PCC point, the AC virtual impedance is calculated according to the proportional relationship. S3. Each energy storage unit in the DC sub-network adopts RC+R parallel virtual impedance droop control, which comprises a DC virtual impedance calculation module, a reference voltage calculation module and a DC voltage tracking control module. S3-1 The DC virtual impedance calculation module calculates the parallel virtual resistance, the series virtual capacitance and the series virtual resistance of the energy storage unit according to the total static power and the total dynamic power of the DC sub-network, the static power and the dynamic power of the lower energy storage converter unit, and the equivalent virtual resistance, the equivalent virtual capacitance and the corresponding time constant of the DC sub-network; S3-2 The reference voltage calculation module calculates the reference voltage according to the rated voltage of the DC sub-network, the output current of the energy storage unit in the DC sub-network and the corresponding virtual resistance and capacitance; S3-3 The DC voltage tracking control module obtains the duty cycle of the switch tube according to the reference voltage of the energy storage unit in the DC sub-network, the battery voltage at the input side and the output current, so that the output voltage changes according to the reference voltage instruction value under the switch control; S4. The interconnection converter connected to each DC sub-network adopts a network-forming control strategy, which comprises an instruction angle calculation module, a voltage amplitude calculation module, a virtual impedance control module and an AC voltage tracking control module; S4-1 The instruction angle calculation module calculates the AC side reference frequency instruction according to the DC side voltage of the interconnection converter connected to the DC sub-network and the mapping parameter, and then obtains the phase angle through the integrator according to the frequency; S4-2 The instruction voltage amplitude calculation module calculates the voltage amplitude reference value according to the reactive power of the AC output of the interconnection converter connected to the DC sub-network and the droop coefficient; calculates the impedance drop compensation according to the three-phase current of the AC output, the resistance and the inductance of the AC feeder and the virtual impedance; and then superimposes the drop compensation and the voltage amplitude reference value to obtain the AC voltage amplitude instruction of the interconnection converter. S4-3 Virtual impedance control module, according to the DC sub-network connected to the interconnected converter AC voltage amplitude instruction, after virtual impedance compensation, calculate the d / q axis instruction of the voltage input AC voltage tracking module; S4-4 AC voltage tracking control module, according to the d / q axis instruction of the voltage of the DC sub-network connected to the interconnected converter, the d / q axis component of the actual three-phase output voltage and output current, calculate the d / q axis component of the modulation wave voltage through the AC voltage tracking control and make the d / q axis component of the actual interconnected converter output voltage change according to the corresponding voltage instruction; S5 generates six-way PWM signal of AC ILC according to the modulation wave voltage.

2. The method of claim 1, wherein, The i-th DC subnetwork equivalent virtual resistance of the calculation of step S1 and the i-th DC subnetwork equivalent virtual capacitance Specifically: (1) wherein is the total static power capacity of all energy storage devices of the i-th DC subgrid, is the rated DC voltage of the i-th DC subgrid; is the actual DC voltage of the i-th DC subgrid, is the DC voltage deviation of the i-th DC subgrid, is the maximum allowed DC voltage deviation amount, is the total dynamic power capacity of all energy storage devices of the i-th DC subgrid; is the maximum allowed value of the normalized change rate of the DC voltage deviation, and the maximum allowed change rates of the normalized change rates of the DC voltage deviations of all DC subgrids are equal.

3. The method of claim 1, wherein, Step S2 calculates the i-th AC subnetwork virtual impedance with The proportional relationship is specifically: (2) In the formula Ri is the resistance of the feeder between the PCC points of the i-th AC subnetwork, L, is the inductance of the feeder between the PCC points of the i-th AC subnetwork.

4. The method of claim 1, wherein, Step S3-1 calculates the parallel virtual resistance of the jth energy storage unit of the ith direct current subnetwork the series virtual capacitance and the series virtual resistance Specifically: (3) wherein and Pstat, i j and Pdyn, i j are the static and dynamic power of the i-th DC subgrid energy storage converter unit j, respectively, is a time constant.

5. The method of claim 1, wherein, The calculation reference voltage of step S3-2 Specifically: (4) wherein is the output current of the jth energy storage unit of the ith DC subgrid, is is the representation in the frequency domain; is is the representation in the frequency domain; is is the representation in the frequency domain.

6. The method of claim 1, wherein, If the converter connected to the energy storage unit is a boost converter, the DC voltage tracking control of step S3-3 can adopt a DC voltage and current double closed loop control, and the duty cycle d of the switching tube of the boost converter is ij The calculation method is: (5) In the formula is the input side battery voltage of the jth energy storage converter in the ith direct current sub-network, is the switching tube duty cycle, is the filter inductance current; is the current inner loop reference value; , are the proportional coefficient and integral coefficient of the direct current voltage outer loop respectively; , are the proportional coefficient and integral coefficient of the direct current inner loop respectively.

7. The method of claim 1, wherein, The AC side reference frequency command of step S4-1 The calculation of the phase angle obtained by the integrator is as follows: The calculation of the phase angle obtained by the integrator is as follows: (6) In the formula is a mapping parameter of the direct current sub-net output voltage and the alternating current frequency; mod(x, 2 ) is the remainder of x divided by 2 .

8. The method of claim 1, wherein, The voltage amplitude reference value of the interconnection converter in step S4-2 Specifically: (7) wherein is the voltage rated amplitude at the AC side subnetwork interconnection converter, is the AC output reactive power, is the droop coefficient; Impedance drop compensation of interconnect converter , The calculation method is as follows: First, output the three-phase AC current. , , Through the following Transformation matrix Converted to d-axis and q-axis components of AC output three-phase current , (8) Then the actual impedance of the line , , the virtual impedance , and the line actual impedance , are calculated , : (9) Alternating voltage amplitude command The calculation method is: (10) Wherein, LPF(x) is low pass filtering x.

9. The method of claim 1, wherein, The d-axis and q-axis instructions of the input AC voltage tracking module voltage described in step S4-3 and Specifically: (11) The AC voltage tracking control of the interconnected converter i in step S4-4 and the output of the d-axis and q-axis components of the modulation wave voltage can adopt AC voltage and current double closed loop control, specifically: According to the AC voltage loop equation, the output quantity is obtained , (12) In the formula and is the output voltage of the interconnection converter i , , is the d-axis and q-axis components converted by formula (8), and are the d-axis and q-axis command values of the current inner loop of the interconnection converter i, is the AC filter capacitor of the interconnection converter i, and are the proportional coefficient and integral coefficient of the AC voltage outer loop of the interconnection converter i, respectively; The AC current closed loop control is specifically: (13) wherein and are the d-axis and q-axis components of the i-modulation wave voltage of the interlinking converter i, respectively, is the ac filter inductance of the interlinking converter i, and are the current inner loop proportional and integral coefficients of the interlinking converter i, respectively.

10. The method of claim 1, wherein, The step S5 generates AC modulation pulse signal specifically: Firstly , The modulation wave voltage of the interconnection converter is obtained by dq to abc conversion , , : (14) The three-phase modulation wave voltage is then divided by half of the voltage of the corresponding direct current sub-network respectively to perform normalization to obtain a modulation signal , , , : (15) Finally, a triangular carrier signal with a frequency fc is generated , the modulation signal , , with a comparison signal to generate a six-way PWM pulse signal for the upper bridge arm and the lower bridge arm . (16)。

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