A self-energystoring type electric energy regulating and controlling equipment for chain micro-grid cluster energy supply system

Abstract

The application relates to a self-energy storage type electric energy regulating and controlling equipment for a chain micro-grid group power supply system, which comprises a modular multilevel energy storage module adopting a back-to-back topology structure, each phase containing an upper bridge arm and a lower bridge arm, each upper bridge arm and lower bridge arm being connected to a direct-current bus, the upper bridge arm and the lower bridge arm being identical in structure and each comprising a plurality of series-connected sub-modules, and each sub-module being provided with an energy storage unit; a parallel side control module used for adopting a power suppression control strategy to the parallel side of the modular multilevel energy storage module to suppress input power fluctuation; and a series side control module used for adopting a natural power flow control mode and a power regulating control mode to the series side of the modular multilevel energy storage module to regulate voltage in a line and active power and reactive power on the line. The application can improve chain micro-grid group power supply reliability.

Description

Technical Field

[0001] This invention relates to the fields of power systems and power electronics, and in particular to a self-storage type power regulation equipment for chain-type microgrid group power supply systems. Background Technology

[0002] As the "last mile" of power supply, the power distribution network plays an extremely important role and must be deeply integrated into local development, serving and supporting high-quality economic and social development and industrial transformation and upgrading, and continuously improving its support and guarantee capabilities, comprehensive carrying capacity, high-quality service capabilities, and transformation and development regulation capabilities. Due to the influence of multiple factors such as geographical location and climate, the power grid structure has not yet extended to end users. Border defense posts currently mainly rely on diesel engines and photovoltaic power supply, which makes it difficult to guarantee the high reliability and high quality of energy demand.

[0003] Existing patent publication CN105591562A discloses a modular multilevel converter. This structure is installed in the transmission line and cannot directly suppress power fluctuations at the new energy grid connection point. Power containing fluctuation components flowing into the transmission network will exacerbate the risk of line power flow exceeding the limit. At the same time, intermittent fluctuation components flowing into the multi-stage step-up transformer will increase the thermal stress and electrical stress of the transformer, accelerate insulation aging, and affect the service life. In addition, the control mode on the series side is relatively simple and cannot perform reasonable mode switching. Summary of the Invention

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

[0005] The technical solution adopted by this invention to solve its technical problem is: to provide a self-storage type power regulation equipment, comprising:

[0006] The modular multilevel 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 a DC bus. The upper bridge arm and lower bridge arm have the same structure and include multiple sub-modules connected in series. Each sub-module is equipped with an energy storage unit.

[0007] The parallel-side control module is used to employ a power smoothing control strategy on the parallel side of the modular multilevel energy storage module to smooth out input power fluctuations.

[0008] The series-side control module is used to apply natural power flow control mode and power regulation control mode to the series side of the modular multilevel energy storage module to regulate the voltage and active and reactive power in the line.

[0009] The submodule includes a half-bridge structure 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.

[0010] The half-bridge structure includes a first IGBT and a second IGBT connected in series. A first diode with reverse polarity is connected in parallel across the two ends of the first IGBT, and a second diode with reverse polarity is connected in parallel across the two ends of the second IGBT. A submodule capacitor is connected in parallel across the two ends of the first and second IGBTs connected in series, and the submodule 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 and a second MOSFET connected in series. A third diode with reverse polarity is connected in parallel across the two ends of the first MOSFET, and a fourth diode with reverse polarity is connected in parallel across the two ends of the second MOSFET. The energy storage unit is also connected in parallel across the two ends of the second MOSFET.

[0012] Each upper and 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, and the current control loop generates the duty cycle of the converter on the parallel side of the modular multilevel energy storage module based on the current reference value.

[0014] The power control loop passes through Generate a current reference value, where, and These are the d-axis and q-axis components of the current reference value for phasor U1, respectively. and These are the d-axis and q-axis components of the line voltage for phasor U1, respectively. and These are the active power fluctuation and reactive power fluctuation rate that need to be smoothed, respectively, expressed as: ,in, and These represent the active and reactive components of the node's fluctuating power, respectively. and These represent the active power and reactive power required by the power transmission network, respectively.

[0015] The current control loop passes through The duty cycle of the converter on the parallel side of the modular multilevel energy storage module is generated, wherein, and The duty cycle of the converter on the parallel side of the modular multilevel energy storage module. and These are the transfer functions of the current loop controller on the d-axis and q-axis, respectively. and These are the d-axis and q-axis components of the current reference value for phasor U1, respectively. and These are the d-axis and q-axis components of the line current obtained from the measurement of phasor U1, respectively. and These are the d-axis and q-axis components of the feedforward voltage of phasor U1, respectively. For coupling quantity, It is a DC voltage.

[0016] The series-side control module includes a voltage outer loop control section, which controls via... Generate the current reference value for the inner current loop, where, and These are the d-axis and q-axis components of the current reference value for the inner current loop, respectively. The d-axis component of the line voltage reference value for phasor U2. and The d-axis and q-axis components of the line voltage of the measured phasor U2. and These are the proportional coefficient and the integral coefficient, respectively.

[0017] The series-side control module includes a power decoupling control section, which includes a power decoupling control loop and a filter. The power decoupling control loop connects to... The filter generates a feedforward voltage reference value through... Generate a current reference value, where, and These are the d-axis and q-axis components of the reference value of the feedforward voltage of phasor U2, respectively. and These are the transfer functions of the power decoupling control loop on the d-axis and q-axis, respectively. and Let d-axis and q-axis components of the feedforward current reference value of the series converter be represented as follows: , For the turns ratio of a series transformer, and These are the d-axis and q-axis components of the voltage at adjacent nodes of a series transformer, respectively. and These represent the active power and reactive power of the line containing the series transformer, respectively, and are expressed as: , and These are the d-axis and q-axis components of the current in the line where the series transformer is located, respectively. and To measure the d-axis and q-axis components of the feedforward current of the series converter, For coupling quantity, and These represent the d-axis and q-axis components of the output current of the series converter, respectively. and These are the d-axis and q-axis components of the feedforward voltage of the measured phasor U2, respectively. and These are the transfer functions of the filter on the d-axis and q-axis, respectively. This is the coupling quantity.

[0018] Beneficial effects

[0019] By adopting the above-mentioned technical solution, 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, while the series-side control module regulates the voltage amplitude to stabilize line operation through a natural power flow control strategy and precisely regulates the distribution of active and reactive power through a power regulation strategy. This solution can eliminate the impact of power fluctuation components on transformers and transmission lines, improve the power flow distribution of connected transmission lines, alleviate power flow congestion caused by microgrids, and improve the power supply reliability of chain microgrid groups. Attached Figure Description

[0020] Figure 1 This is a topology diagram of the self-storage type power regulation equipment according to an embodiment of the present invention;

[0021] Figure 2 This is a topology diagram of the submodules in an embodiment of the present invention;

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

[0023] Figure 4 This is an overall architecture diagram of the application of the embodiments of the present invention. Detailed Implementation

[0024] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0025] Embodiments of the present invention relate to a self-storage type power regulation device for a chain-type microgrid group power supply system, such as... Figure 1 As shown, it includes:

[0026] The modular multilevel 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 is connected to a DC bus. The upper bridge arm and lower bridge arm have the same structure and include multiple sub-modules (SM) connected in series. Each sub-module is equipped with an energy storage unit. Each upper bridge arm and lower bridge arm can be equipped with a bridge arm reactor.

[0027] The parallel-side control module is used to employ a power smoothing control strategy on the parallel side of the modular multilevel energy storage module to smooth out input power fluctuations.

[0028] The series-side control module is used to apply natural power flow control mode and power regulation control mode to the series side of the modular multilevel energy storage module to regulate the voltage and active and reactive power in the line.

[0029] like Figure 2 As shown, the submodule in this embodiment includes a half-bridge structure 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.

[0030] The half-bridge structure in this embodiment includes a first IGBT Q1 and a second IGBT Q2 connected in series. A first diode with reverse polarity is connected in parallel across the two ends of the first IGBT Q1, and a second diode with reverse polarity is connected in parallel across the two ends of the second IGBT Q2. A submodule capacitor C is connected in parallel across the two ends of the series-connected first IGBT Q1 and second IGBT Q2. sm The submodule capacitor C sm It is connected to the high-voltage side of the non-isolated bidirectional DC / DC converter. By controlling the on and off states of the first IGBT Q1 and the second IGBT Q2, two voltage levels, 0 and E, can be generated between ports A and B. When the first IGBT Q1 is on and the second IGBT Q2 is off, the voltage between ports A and B is equal to the voltage across the submodule capacitor C. sm The voltage across the terminals, when the first IGBT Q1 is off and the second IGBT Q2 is on, is the voltage across the submodule capacitor C. sm When bypassed, the voltage between ports A and B is 0. If the first IGBT Q1 and the second IGBT Q2 are both turned on, it will affect the submodule capacitor C. smIf a short circuit is formed on the side, it will pose a risk of burning out the submodule. Therefore, the submodule prohibits the first IGBT Q1 and the second IGBT Q2 from being turned on at the same time. This embodiment can avoid the occurrence of capacitor short circuit faults by adding dead time control during the switching process of the first IGBT Q1 and the second IGBT Q2.

[0031] The non-isolated bidirectional DC / DC converter in this embodiment employs a bidirectional Buck-Boost circuit. The bidirectional Buck-Boost circuit includes a first MOSFET Q3 and a second MOSFET Q4 connected in series. A third diode, configured in reverse, is connected in parallel across the first MOSFET Q3, and a fourth diode, configured in reverse, is connected in parallel across the second MOSFET Q4. The energy storage unit is also connected in parallel across the second MOSFET Q4. The bidirectional Buck-Boost circuit in this embodiment can operate in Buck mode and Boost mode. 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 to the modular multilevel converter. In Buck mode, electrical energy flows from the high-voltage submodule capacitor side to the low-voltage energy storage unit, charging the energy storage unit.

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

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

[0034] Parallel converters smooth out power fluctuations at the input nodes, including the active power component. and reactive part In this embodiment, 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, and the current control loop generates the duty cycle of the converter on the parallel side of the modular multilevel energy storage module based on the current reference value.

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

[0036] ;

[0037] In the formula, and The duty cycle of the converter on the parallel side of the modular multilevel energy storage module. and These are the transfer functions of the current loop controller on the d-axis and q-axis, respectively, which can be derived from the proportional coefficient. and integral coefficient Composed of, and satisfying , For operators, and These are the d-axis and q-axis components of the current reference value for phasor U1, respectively. and These are the d-axis and q-axis components of the line current obtained from the measurement of phasor U1, respectively. and These are the d-axis and q-axis components of the feedforward voltage of phasor U1, respectively. For coupling quantity, It is a DC voltage.

[0038] The power control loop calculates the difference between the power at the input node containing fluctuation components and the power required by the transmission network to obtain the fluctuation amount that the parallel converter needs to smooth, i.e. ,in, and These refer to the active power fluctuation and reactive power fluctuation rate that need to be smoothed out, respectively. and These represent the active and reactive power required by the transmission network, respectively. The power control loop can be represented as:

[0039] ;

[0040] in, and These are the d-axis and q-axis components of the line voltage of phasor U1, respectively.

[0041] The working principle of the natural current 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 phasor U1, The reference value of phasor U2 in the dq coordinate system is:

[0043] ;

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

[0045] The series-side control module in this embodiment includes a voltage outer loop control section, which generates a current reference value fed into the current inner loop, and can be expressed as:

[0046] ;

[0047] in, and These are the d-axis and q-axis components of the current reference value for the inner current loop, respectively. and The d-axis and q-axis components of the line voltage of the measured phasor U2. and These 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 section, 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 instantaneous power theory. Series The active and reactive power of the line generate the reference value of the feedforward voltage.

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

[0052] ;

[0053] In the formula, and These are series transformers T Series The d-axis and q-axis components of the voltage at adjacent nodes. and These are series transformers T Series The d-axis and q-axis components of the current in the line.

[0054] Assuming series transformer T Series The ratio of According to the series transformer T Series The active and reactive power of the line can be used to obtain the d-axis and q-axis components of the feedforward current reference value of the series converter. The calculation method is as follows:

[0055] ;

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

[0057] By combining the average model with a traditional PI controller, the reference value of the feedforward voltage output of the power decoupling control loop can be obtained. Its calculation method is as follows:

[0058] ;

[0059] In the formula, and These are the d-axis and q-axis components of the reference value of the feedforward voltage of phasor U2, respectively. and These 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 integral coefficient Composed of, and satisfying , and To measure the d-axis and q-axis components of the feedforward current of the series converter, For coupling quantity, This is the equivalent inductance of the line.

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

[0061] ;

[0062] In the formula, and These represent the d-axis and q-axis components of the output current of the series converter, respectively. and These are the d-axis and q-axis components of the feedforward voltage of the measured phasor U2, respectively. For coupling quantity, and Let be the transfer functions of the filter on the d-axis and q-axis, respectively, which are determined by the scaling factor. and integral coefficient Composed of, and satisfying .

[0063] The self-storage power regulation equipment in this embodiment can dynamically compensate for input power fluctuations through parallel power smoothing control. The series converter flexibly switches between natural power flow control mode and power regulation control mode. When the line power fluctuation is severe or the power flow distribution is uneven, the natural power flow control mode stabilizes the line operation by adjusting the voltage amplitude, while the power regulation control mode precisely adjusts the distribution of active and reactive power through the decoupling control loop, thereby suppressing voltage fluctuations and power flow congestion at the interconnected nodes of the microgrid. When the system tends to stabilize or the fluctuations decrease, the parallel control gradually reduces the compensation intensity, and the series control switches to the natural power flow control mode to maintain efficient energy transmission, realizing highly reliable power supply and flexible mutual assistance for the chain microgrid.

[0064] The self-storage power regulation equipment of this embodiment can be applied to the interconnection architecture of chain-type microgrids, and its overall architecture diagram is as follows. Figure 4 As shown, it can eliminate the impact of power fluctuation components on transformers and transmission lines, improve the power flow distribution of connected transmission lines, and alleviate power flow congestion caused by microgrids.

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

Claims

1. A self-storage type power regulation equipment, characterized in that, include: The modular multilevel 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 a DC bus. The upper bridge arm and lower bridge arm have the same structure and include multiple sub-modules connected in series. Each sub-module is equipped with an energy storage unit. The parallel-side control module is used to employ a power smoothing control strategy on the parallel side of the modular multilevel energy storage module to smooth input power fluctuations. 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, and the current control loop generates the duty cycle of the converter on the parallel side of the modular multilevel energy storage module based on the current reference value. The power control loop... Generate a current reference value, where i 1dref and i 1qref These are the d-axis and q-axis components of the current reference value of phasor U1, respectively. 1d and u 1q These are the d-axis and q-axis components of the line voltage for phasor U1, respectively, ΔP w and ΔQ w These are the active power fluctuation and reactive power fluctuation rate that need to be smoothed, respectively, expressed as: Among them, P w and Q w These represent the active and reactive components of the node's fluctuating power, P. wref and Q wref These are the active power and reactive power required by the power transmission network, respectively. A series-side control module is used to apply natural power flow control mode and power regulation control mode to the series side of the modular multilevel energy storage module to regulate the voltage and active and reactive power in the line. The series-side control module includes a power decoupling control section, which comprises a power decoupling control loop and a filter. The power decoupling control loop... The filter generates a feedforward voltage reference value through... Generate a current reference value, where u′ 2dref and u′ 2qref G represents the d-axis and q-axis components of the reference value of the feedforward voltage of phasor U2, respectively. sd () and G sq ( ) represent the transfer functions of the power decoupling control loop on the d-axis and q-axis, respectively, i′ 2dref and i′ 2qref Let d-axis and q-axis components of the feedforward current reference value of the series converter be represented as follows: k is the turns ratio of the series transformer, u 3d and u 3q These are the d-axis and q-axis components of the voltage at adjacent nodes of a series transformer, respectively. line and Q line These represent the active power and reactive power of the line containing the series transformer, respectively, and are expressed as: i 3d and i 3q These are the d-axis and q-axis components of the current in the line where the series transformer is located, respectively, i′ 2d and i′ 2q To measure the d-axis and q-axis components of the feedforward current of the series converter, ωL R For coupling quantity, i 2dref and i 2qref These are the d-axis and q-axis components of the output current of the series converter, respectively, u′ 2d and u′ 2q G represents the d-axis and q-axis components of the feedforward voltage of the measured phasor U2, respectively. vd () and G vq () are the transfer functions of the filter on the d-axis and q-axis, respectively, and ωC2 is the coupling quantity.

2. The self-storage type power regulation equipment according to claim 1, characterized in that, The submodule includes a half-bridge structure 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.

3. The self-storage type power regulation equipment according to claim 2, characterized in that, The half-bridge structure includes a first IGBT and a second IGBT connected in series. A first diode with reverse polarity is connected in parallel across the two ends of the first IGBT, and a second diode with reverse polarity is connected in parallel across the two ends of the second IGBT. A submodule capacitor is connected in parallel across the two ends of the first and second IGBTs connected in series, and the submodule capacitor is connected to the high-voltage side of the non-isolated bidirectional DC / DC converter.

4. The self-storage type power regulation 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 and a second MOSFET connected in series. A third diode with reverse polarity is connected in parallel across the two ends of the first MOSFET, and a fourth diode with reverse polarity is connected in parallel across the two ends of the second MOSFET. The energy storage unit is also connected in parallel across the two ends of the second MOSFET.

5. The self-storage type power regulation equipment according to claim 1, characterized in that, Each upper and lower bridge arm is equipped with a bridge arm reactor.

6. The self-storage type power regulation equipment according to claim 1, characterized in that, The current control loop passes through Generate the duty cycle of the converter on the parallel side of the modular multilevel energy storage module, where d 1d and d 1q G represents the duty cycle of the converter on the parallel side of the modular multilevel energy storage module. d () and G q () represent the transfer functions of the current loop controller on the d-axis and q-axis, respectively. 1d and i 1q These are the d-axis and q-axis components of the line current obtained from the measurement of phasor U1, u′ and u′, respectively. 1d and u′ 1q These are the d-axis and q-axis components of the feedforward voltage of phasor U1, respectively, where ωL1 is the coupling quantity, U dc It is a DC voltage.

7. The self-storage type power regulation equipment according to claim 1, characterized in that, The series-side control module includes a voltage outer loop control section, which controls via... Generate the current reference value for the inner current loop, where i sedref and i seqref These are the d-axis and q-axis components of the current reference value for the inner current loop, respectively. 2dref The d-axis component of the line voltage reference value for phasor U2, u 2d and u 2q To obtain the d-axis and q-axis components of the line voltage of the measured phasor U2, k p1 and k i1 These are the proportional coefficient and the integral coefficient, respectively.

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