Self-energy-storage type electric energy regulation and control equipment for chain type micro-grid group energy supply system

Abstract

The invention relates to a self-energy-storage type electric energy regulation and control device for a chain type micro-grid group energy supply system, and the device comprises a modularized multi-level energy storage module which is of a back-to-back topological structure, each phase comprises an upper bridge arm and a lower bridge arm, each upper bridge arm and each lower bridge arm are connected to a DC bus, and the modularized multi-level energy storage module is connected to the DC bus; the upper bridge arm and the lower bridge arm have the same structure and each comprise a plurality of submodules which are connected in series, and each submodule is provided with an energy storage unit; the parallel side control module is used for adopting a power stabilizing control strategy on the parallel side of the modularized multi-level energy storage module to stabilize input power fluctuation; and the series side control module is used for adopting a natural power flow control mode and a power regulation and control mode on the series side of the modularized multi-level energy storage module so as to regulate the voltage in the line and the active power and the reactive power on the line. According to the invention, the power supply reliability of the chain-type microgrid group can be improved.

Description

Technical Field

[0001] The present invention relates to the field of power systems and power electronics technology, and in particular to a self-storage electric energy control equipment for a chain microgrid energy supply system. Background Art

[0002] As the "last mile" of power supply, the distribution network plays a crucial role and holds a crucial position. It must be deeply integrated into local development, serving to support high-quality economic and social development and industrial transformation and upgrading. It must continuously enhance its support and guarantee capabilities, comprehensive carrying capacity, high-quality service capabilities, and the ability to regulate transformation and development. Due to multiple factors, such as geographic location and climate, the power grid has yet to reach end users. Border defense garrisons currently rely primarily on diesel engines and photovoltaic power generation, making it difficult to guarantee high-reliability and high-quality energy demand.

[0003] Existing patent publication CN105591562A discloses a modular multilevel converter. This structure, installed in a transmission line, cannot directly smooth out power fluctuations at the renewable energy grid connection point. Power containing fluctuating components flowing into the transmission network increases the risk of line current exceeding limits. Intermittent fluctuating components flowing into a multi-stage step-up transformer increase the transformer's thermal and electrical stresses, accelerate insulation aging, and impact its service life. Furthermore, the control mode on the series side is relatively simple, preventing reasonable mode switching. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a self-storage electric energy control equipment for a chain microgrid group energy supply system, which can improve the power supply reliability of the chain microgrid group.

[0005] The technical solution adopted by the present invention to solve the technical problem is to provide a self-storage type electric energy control equipment, including:

[0006] A modular multi-level energy storage module adopts a back-to-back topology. Each phase includes an upper bridge arm and a lower bridge arm. Each upper bridge arm and lower bridge arm are connected to the DC bus. The upper bridge arm and the lower bridge arm have the same structure and both include multiple sub-modules connected in series, and each sub-module is equipped with an energy storage unit.

[0007] A parallel side control module, configured to adopt a power smoothing control strategy on the parallel side of the modular multi-level energy storage module to smooth input power fluctuations;

[0008] The series side control module is used to adopt a natural power flow control mode and a power regulation control mode on the series side of the modular multi-level energy storage module to adjust the voltage in the line and the active power and reactive power on the line.

[0009] The submodule includes a half-bridge structure part and a non-isolated bidirectional DC / DC converter. The low-voltage side of the non-isolated bidirectional DC / DC converter is connected to the energy storage unit, and the high-voltage side is connected to the half-bridge structure part.

[0010] The half-bridge structure includes a first IGBT tube and a second IGBT tube connected in series, with a first diode arranged in reverse direction connected in parallel at both ends of the first IGBT tube, and a second diode arranged in reverse direction connected in parallel at both ends of the second IGBT tube; a sub-module capacitor is connected in parallel at both ends of the first IGBT tube and the second IGBT tube connected in series, and the sub-module capacitor is connected to the high-voltage side of the non-isolated bidirectional DC / DC converter.

[0011] The non-isolated bidirectional DC / DC converter adopts a bidirectional Buck-Boost circuit, which includes a first MOSFET tube and a second MOSFET tube connected in series. A third diode arranged in reverse direction is connected in parallel at both ends of the first MOSFET tube, and a fourth diode arranged in reverse direction is connected in parallel at both ends of the second MOSFET tube; and the energy storage unit is also connected in parallel at both ends of the second MOSFET tube.

[0012] Each of the upper bridge arm and the lower bridge arm is equipped with a bridge arm reactor.

[0013] The parallel side control module includes a power control loop and a current control loop. The power control loop generates a current reference value based on the fluctuating power of the node. The current control loop generates a duty cycle of the converter on the parallel side of the modular multi-level energy storage module based on the current reference value.

[0014] The power control loop is Generates a current reference value where and are the d-axis component and q-axis component of the current reference value of phase U1, and are the d-axis component and q-axis component of the line voltage of phase U1, and are the active power fluctuation and reactive power fluctuation rate that need to be smoothed, expressed as: ,in, and are the active and reactive parts of the node’s fluctuating power, and are the active power and reactive power required by the transmission grid, respectively.

[0015] The current control loop is Generate a duty cycle of the converter on the parallel side of the modular multi-level energy storage module, wherein: and is the duty cycle of the converter on the parallel side of the modular multi-level energy storage module, and are the transfer functions of the current loop controller on the d-axis and q-axis respectively, and are the d-axis component and q-axis component of the current reference value of phase U1, and are the d-axis component and q-axis component of the line current of the measured phase quantity U1, and are the d-axis component and q-axis component of the feedforward voltage of phasor U1, is the coupling amount, is a DC voltage.

[0016] The series side control module includes a voltage outer loop control part, and the voltage outer loop control part is controlled by Generate the current reference value of the current inner loop, where and They are the d-axis component and q-axis component of the current reference value of the inner current loop, is the d-axis component of the reference value of the line voltage of phase U2, and are the d-axis and q-axis components of the line voltage of the measured phase quantity U2, and are the proportional coefficient and the integral coefficient respectively.

[0017] The series side control module includes a power decoupling control part, which includes a power decoupling control loop and a filter. Generates a feedforward voltage reference, the filter passes Generates a current reference value where and are the d-axis component and q-axis component of the reference value of the feedforward voltage of phase U2, and are the transfer functions of the power decoupling control loop on the d-axis and q-axis respectively, and are the d-axis component and q-axis component of the feedforward current reference value of the series converter, respectively, expressed as: , is the series transformer ratio, and are the d-axis component and q-axis component of the voltage of the adjacent nodes of the series transformer, and are the active power and reactive power of the line where the series transformer is located, respectively, expressed as: , and are the d-axis component and q-axis component of the line current where the series transformer is located, and are the measured d-axis and q-axis components of the feedforward current of the series converter, is the coupling amount, and are the d-axis component and q-axis component of the output current of the series converter, and are the d-axis component and q-axis component of the feedforward voltage of the measured phase quantity U2, and are the transfer functions of the filter on the d-axis and q-axis respectively, is the coupling amount.

[0018] Beneficial effects

[0019] Due to the adoption of the above-mentioned technical scheme, the present invention has the following advantages and positive effects compared with the prior art: the present invention introduces a parallel side control module and a series side control module. The parallel side control module dynamically compensates for the input power fluctuation component through a power smoothing control strategy. The series side control module adjusts the voltage amplitude to stabilize the line operation through a natural flow control strategy, and accurately adjusts the distribution of active power and reactive power through a power regulation strategy. This scheme can eliminate the influence of the power fluctuation component on the transformer and the transmission line, improve the flow distribution of the connected transmission lines, alleviate the flow congestion caused by the microgrid, and improve the power supply reliability of the chain microgrid group. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a topological diagram of a self-storage type electric energy control equipment according to an embodiment of the present invention;

[0021] Figure 2 It is a topological structure diagram of the submodule in an embodiment of the present invention;

[0022] Figure 3 This is a control block diagram of a self-storage type electric energy control equipment according to an embodiment of the present invention;

[0023] Figure 4 It is an overall architecture diagram when the embodiment of the present invention is applied. DETAILED DESCRIPTION

[0024] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0025] The embodiment of the present invention relates to a self-storage type power control equipment for a chain microgrid group energy supply system, such as Figure 1 As shown, including:

[0026] A modular multi-level energy storage module adopts a back-to-back topology. Each phase includes an upper arm and a lower arm. Each upper arm and lower arm are connected to the DC bus. The upper and lower arms have the same structure and each includes multiple sub-modules (SMs) connected in series. Each sub-module is equipped with an energy storage unit. Each upper arm and lower arm can be equipped with an arm reactor.

[0027] A parallel side control module, configured to adopt a power smoothing control strategy on the parallel side of the modular multi-level energy storage module to smooth input power fluctuations;

[0028] The series side control module is used to adopt a natural power flow control mode and a power regulation control mode on the series side of the modular multi-level energy storage module to adjust the voltage in the line and the active power and reactive power on the line.

[0029] like Figure 2 As shown, the submodule in this embodiment includes a half-bridge structure part and a non-isolated bidirectional DC / DC converter, the low-voltage side of the non-isolated bidirectional DC / DC converter is connected to the energy storage unit, and the high-voltage side is connected to the half-bridge structure part.

[0030] The half-bridge structure in this embodiment includes a first IGBT tube Q1 and a second IGBT tube Q2 connected in series. A first diode arranged in reverse direction is connected in parallel at both ends of the first IGBT tube Q1, and a second diode arranged in reverse direction is connected in parallel at both ends of the second IGBT tube Q2. A submodule capacitor C is connected in parallel at both ends of the first IGBT tube Q1 and the second IGBT tube Q2. sm , the submodule capacitance C sm Connected to the high-voltage side of the non-isolated bidirectional DC / DC converter. By controlling the on and off of the first IGBT tube Q1 and the second IGBT tube Q2, two levels of 0 and E can be formed between the A port and the B port. When the first IGBT tube Q1 is turned on and the second IGBT tube Q2 is turned off, the voltage between the A port and the B port is equal to the submodule capacitor C. sm The voltage across the two ends, when the first IGBT tube Q1 is turned off and the second IGBT tube Q2 is turned on, the submodule capacitor C sm Bypassed, the voltage between port A and port B is 0. If the first IGBT tube Q1 and the second IGBT tube Q2 are turned on at the same time, the submodule capacitor C smA short-circuit channel is formed on the side, which will bring the risk of burning to the sub-module. Therefore, the sub-module prohibits the first IGBT tube Q1 and the second IGBT tube Q2 from being turned on at the same time. This embodiment can avoid the occurrence of capacitor short-circuit faults by adding dead-zone control during the switching process of the first IGBT tube Q1 and the second IGBT tube Q2.

[0031] The non-isolated bidirectional DC / DC converter in this embodiment uses a bidirectional Buck-Boost circuit. The bidirectional Buck-Boost circuit includes a first MOSFET tube Q3 and a second MOSFET tube Q4 connected in series. A third diode arranged in opposite directions is connected in parallel at both ends of the first MOSFET tube Q3, and a fourth diode arranged in opposite directions is connected in parallel at both ends of the second MOSFET tube Q4. The energy storage unit is also connected in parallel at both ends of the second MOSFET tube Q4. The bidirectional Buck-Boost circuit in this embodiment can operate in Buck mode and Boost mode. When in Boost mode, electrical energy flows from the low-voltage energy storage unit side to the high-voltage submodule capacitor side, enabling the energy storage unit to discharge into the modular multilevel converter. When in Buck mode, electrical energy flows from the high-voltage submodule capacitor side to the low-voltage energy storage unit, enabling the energy storage unit to charge.

[0032] Figure 3 This is a control block diagram of the self-storage electric energy regulation equipment of this embodiment, wherein the parallel side adopts a power leveling control strategy, and the series side adopts a natural flow control mode and a power regulation control mode.

[0033] The working principle of the power leveling control strategy is as follows:

[0034] The parallel converter smoothes the power with fluctuating components at the input node, including the active part. and reactive part The parallel-side control module in this embodiment includes a power control loop and a current control loop. The power control loop generates a current reference value based on the fluctuating power of the node, and the current control loop generates a duty cycle of the converter on the parallel side of the modular multi-level energy storage module based on the current reference value.

[0035] In order to improve the control performance of the parallel converter, the feedforward voltage term and the current decoupling term are added to its current control loop. The current control loop can be expressed as:

[0036] ;

[0037] Where, and is the duty cycle of the converter on the parallel side of the modular multi-level energy storage module, and are the transfer functions of the current loop controller on the d-axis and q-axis, respectively, which can be expressed by the proportional coefficient and the integral coefficient Composition and satisfaction , is the operator, and are the d-axis component and q-axis component of the current reference value of phase U1, and are the d-axis component and q-axis component of the line current of the measured phase quantity U1, and are the d-axis component and q-axis component of the feedforward voltage of phasor U1, is the coupling amount, is a DC voltage.

[0038] The power control loop takes the difference between the power of the input node containing the fluctuation component and the power required by the transmission network to obtain the fluctuation amount that the parallel converter needs to smooth out, that is, ,in, and are the active power fluctuation and reactive power fluctuation rate that need to be smoothed, and are the active power and reactive power required by the transmission network respectively. The power control loop can be expressed as:

[0039] ;

[0040] in, and They are the d-axis component and q-axis component of the line voltage of phase U1 respectively.

[0041] The working principle of the natural flow control mode in this embodiment is as follows:

[0042] When the d-axis of the two-phase stationary coordinate system is fixed in the direction of the phase quantity U1, , then the reference value of phase U2 in dq coordinate is:

[0043] ;

[0044] in, is the d-axis component of the reference value of the line voltage of phase U2, is the q-axis component of the reference value of the line voltage of phasor U2, represents the proportionality constant.

[0045] The series side control module in this embodiment includes a voltage outer loop control part, which is used to generate a current reference value fed into the current inner loop, which can be expressed as:

[0046] ;

[0047] in, and They are the d-axis component and q-axis component of the current reference value of the inner current loop, and are the d-axis and q-axis components of the line voltage of the measured phase quantity U2, and are the proportional coefficient and the integral coefficient respectively.

[0048] The working principle of the power regulation control mode in this embodiment is as follows:

[0049] The series-side control module in this embodiment includes a power decoupling control part, which includes a power decoupling control loop and a filter.

[0050] In the power decoupling control loop, the series transformer T is calculated based on the instantaneous power theory. Series The active and reactive power generation on the line generates the feed-forward voltage reference.

[0051] Among them, the series transformer T Series Active power of the line and reactive power is calculated as follows:

[0052] ;

[0053] Where, and They are respectively series transformers T Series The d-axis component and q-axis component of the adjacent node voltage, and They are respectively series transformers T Series The d-axis component and q-axis component of the line current.

[0054] Assume that the series transformer T Series The transformation ratio is , according to the series transformer T Series The active power and reactive power of the line can be used to obtain the d-axis component and q-axis component of the feedforward current reference value of the series converter, which are calculated as follows:

[0055] ;

[0056] in, and They are the d-axis component and q-axis component of the feedforward current reference value of the series converter respectively.

[0057] Combining the average model with the traditional PI controller, the feedforward voltage reference value output by the power decoupling control loop can be obtained, which is calculated as follows:

[0058] ;

[0059] Where, and are the d-axis component and q-axis component of the reference value of the feedforward voltage of phase U2, and are the transfer functions of the power decoupling control loop on the d-axis and q-axis, respectively, which are determined by the proportional coefficient and the integral coefficient Composition and satisfaction , and are the measured d-axis and q-axis components of the feedforward current of the series converter, is the coupling amount, is the equivalent inductance of the line.

[0060] In the subsequent filter, decoupling is performed by adding a feedforward term. The filter can be expressed as:

[0061] ;

[0062] Where, and are the d-axis component and q-axis component of the output current of the series converter, and are the d-axis component and q-axis component of the feedforward voltage of the measured phase quantity U2, is the coupling amount, and are the transfer functions of the filter in the d-axis and q-axis, respectively, which are determined by the proportional coefficient and the integral coefficient Composition and satisfaction .

[0063] The self-storage electric energy control equipment of this embodiment can dynamically compensate for the input power fluctuation component through parallel power smoothing control. The series converter flexibly switches between the natural flow control mode and the power control mode. When the line power fluctuates violently or the flow distribution is uneven, the natural flow control mode stabilizes the line operation by adjusting the voltage amplitude, and the power control mode accurately adjusts the active and reactive power distribution through the decoupling control loop, thereby suppressing the voltage fluctuation and flow congestion of the interconnected nodes of the microgrid group; when the system tends to be stable or the fluctuation decreases, the parallel control gradually reduces the compensation intensity, and the series control switches to the natural flow control mode to maintain efficient energy transmission, thereby realizing high-reliability power supply and flexible mutual assistance of the chain microgrid group.

[0064] The self-storage type electric energy control equipment of this embodiment can be applied to the interconnected architecture of the chain microgrid, and its overall architecture is shown in the figure below. Figure 4 As shown, it is possible to eliminate the impact of power fluctuation components on transformers and transmission lines, improve the power flow distribution of connected transmission lines, and alleviate the power flow congestion caused by microgrids.

[0065] It is worth mentioning that the self-storage power control equipment of this embodiment can be applied to any power supply scenario with long-distance, distributed resource dispersion (such as border areas, mountainous areas, offshore fishing grounds, islands and remote towns). This embodiment is not limited to the use of 10kV and 35kV voltage transmission networks, and the access of each sub-microgrid is not limited to energy storage units and renewable energy.

Claims

1. A self-storage type electric energy control equipment, characterized in that: include: A modular multi-level energy storage module adopts a back-to-back topology. Each phase includes an upper bridge arm and a lower bridge arm. Each upper bridge arm and lower bridge arm are connected to the DC bus. The upper bridge arm and the lower bridge arm have the same structure and both include multiple sub-modules connected in series, and each sub-module is equipped with an energy storage unit. A parallel side control module, configured to adopt a power smoothing control strategy on the parallel side of the modular multi-level energy storage module to smooth input power fluctuations; The series side control module is used to adopt a natural power flow control mode and a power regulation control mode on the series side of the modular multi-level energy storage module to adjust the voltage in the line and the active power and reactive power on the line.

2. The self-storage type electric energy control equipment according to claim 1, characterized in that: The submodule includes a half-bridge structure part and a non-isolated bidirectional DC / DC converter. The low-voltage side of the non-isolated bidirectional DC / DC converter is connected to the energy storage unit, and the high-voltage side is connected to the half-bridge structure part.

3. The self-storage type electric energy control equipment according to claim 2, characterized in that: The half-bridge structure includes a first IGBT tube and a second IGBT tube connected in series, with a first diode arranged in reverse direction connected in parallel at both ends of the first IGBT tube, and a second diode arranged in reverse direction connected in parallel at both ends of the second IGBT tube; a sub-module capacitor is connected in parallel at both ends of the first IGBT tube and the second IGBT tube connected in series, and the sub-module capacitor is connected to the high-voltage side of the non-isolated bidirectional DC / DC converter.

4. The self-storage type electric energy control equipment according to claim 2, characterized in that: The non-isolated bidirectional DC / DC converter adopts a bidirectional Buck-Boost circuit, which includes a first MOSFET tube and a second MOSFET tube connected in series. A third diode arranged in reverse direction is connected in parallel at both ends of the first MOSFET tube, and a fourth diode arranged in reverse direction is connected in parallel at both ends of the second MOSFET tube; and the energy storage unit is also connected in parallel at both ends of the second MOSFET tube.

5. The self-storage type electric energy control equipment according to claim 1, characterized in that: Each of the upper bridge arm and the lower bridge arm is equipped with a bridge arm reactor.

6. The self-storage type electric energy control equipment according to claim 1, characterized in that: The parallel side control module includes a power control loop and a current control loop. The power control loop generates a current reference value based on the fluctuating power of the node. The current control loop generates a duty cycle of the converter on the parallel side of the modular multi-level energy storage module based on the current reference value.

7. The self-storage type electric energy control equipment according to claim 6, characterized in that: The power control loop is Generates a current reference value where and are the d-axis component and q-axis component of the current reference value of phase U1, and are the d-axis component and q-axis component of the line voltage of phase U1, and are the active power fluctuation and reactive power fluctuation rate that need to be smoothed, expressed as: ,in, and are the active and reactive parts of the node’s fluctuating power, and are the active power and reactive power required by the transmission grid, respectively.

8. The self-storage type electric energy control equipment according to claim 6, characterized in that: The current control loop is Generate a duty cycle of the converter on the parallel side of the modular multi-level energy storage module, wherein: and is the duty cycle of the converter on the parallel side of the modular multi-level energy storage module, and are the transfer functions of the current loop controller on the d-axis and q-axis respectively, and are the d-axis component and q-axis component of the current reference value of phase U1, and are the d-axis component and q-axis component of the line current of the measured phase quantity U1, and are the d-axis component and q-axis component of the feedforward voltage of phasor U1, is the coupling amount, is a DC voltage.

9. The self-storage type electric energy control equipment according to claim 1, characterized in that: The series side control module includes a voltage outer loop control part, and the voltage outer loop control part is controlled by Generate the current reference value of the current inner loop, where and They are the d-axis component and q-axis component of the current reference value of the inner current loop, is the d-axis component of the reference value of the line voltage of phase U2, and are the d-axis and q-axis components of the line voltage of the measured phase quantity U2, and are the proportional coefficient and the integral coefficient respectively.

10. The self-storage type electric energy control equipment according to claim 1, characterized in that: The series side control module includes a power decoupling control part, which includes a power decoupling control loop and a filter. Generates a feedforward voltage reference, the filter passes Generates a current reference value where and are the d-axis component and q-axis component of the reference value of the feedforward voltage of phase U2, and are the transfer functions of the power decoupling control loop on the d-axis and q-axis respectively, and are the d-axis component and q-axis component of the feedforward current reference value of the series converter, respectively, expressed as: , is the series transformer ratio, and are the d-axis component and q-axis component of the voltage of the adjacent nodes of the series transformer, and are the active power and reactive power of the line where the series transformer is located, respectively, expressed as: , and are the d-axis component and q-axis component of the line current where the series transformer is located, and are the measured d-axis and q-axis components of the feedforward current of the series converter, is the coupling amount, and are the d-axis component and q-axis component of the output current of the series converter, and are the d-axis component and q-axis component of the feedforward voltage of the measured phase quantity U2, and are the transfer functions of the filter on the d-axis and q-axis respectively, is the coupling amount.

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