A control method of a multiplex bridge arm energy storage type H-MMC system

Abstract

The application discloses a control method of a multiplex bridge arm energy storage type H-MMC system. The multiplex bridge arm energy storage type H-MMC system comprises an H-MMC, a super capacitor, and two three-phase power systems; the control strategy of the multiplex bridge arm energy storage type H-MMC system is composed of a main modulation wave control strategy, a super capacitor energy storage control strategy, and modulation wave calculation; wherein the main modulation wave control strategy is composed of a primary side power instruction, a hierarchical submodule capacitor voltage stabilizing and equalizing control strategy, and a PIR bridge arm current tracking control strategy; a P control is used to track the rated value of the super capacitor voltage of the i-th bridge arm j-th submodule to obtain the modulation wave of the super capacitor voltage, the S1 / S2 and S3 / S4 in the i-th bridge arm j-th submodule are modulated to obtain positive and negative output port modulation signals, the phase-shifted sinusoidal pulse width modulation is used to obtain the switching signals of S1 / S2 and S3 / S4 in the multiplex bridge arm energy storage type full-bridge submodule, and the control process is completed; the application provides the topology structure and the control strategy of the multiplex bridge arm energy storage type H-MMC system, has the effects of real-time compensation of power grid active impact, improvement of system inertia, good submodule consistency, and cost saving of the multiplex variable current bridge arm energy storage.

Description

Technical Field

[0001] This invention belongs to the field of AC / AC converter energy storage, and specifically relates to a control method for a multiplexed bridge arm energy storage type H-MMC system. Background Technology

[0002] Western and northern my country possess abundant clean energy resources and have established large-scale wind, solar, hydropower, and thermal power generation bases, requiring the efficient supply of these clean energy sources to the power grid. However, the integration of a high proportion of clean energy generation into the grid can lead to power surges. Therefore, installing energy storage devices to reduce active power fluctuations has become an effective means of addressing power surges. Currently, researching how to install energy storage devices to solve the power surge problem has become an important trend.

[0003] Traditional energy storage MMC topologies typically fall into two categories: one connects the energy storage carrier directly in parallel across the submodule capacitor; the other connects the energy storage carrier in parallel across the half-bridge submodule capacitor via a bidirectional DC / DC converter. However, because MMCs have a DC bus and use half-bridge submodules, this topology cannot disconnect the DC signal in the event of a DC fault. In contrast, H-MMC is a direct AC / AC converter that does not have a DC bus and uses full-bridge submodules. Compared to the traditional topology where the bidirectional DC / DC converter is directly connected in parallel across the half-bridge submodule capacitor, H-MMC does not require additional parallel switching devices; it only needs to reuse the bridge arms to achieve bidirectional DC / DC functionality.

[0004] The H-MMC system with multiplexed bridge arms uses full-bridge sub-modules. It does not require additional switching devices. It only needs to connect an energy storage inductor and a supercapacitor in parallel to form a full-bridge energy storage structure with multiplexed bridge arms to realize the energy storage function. However, in order to control the charging and discharging process of the supercapacitor, an additional supercapacitor PI controller is required, which increases the cost. Summary of the Invention

[0005] To address the shortcomings and deficiencies described in the background art above, this invention proposes a control method for a reusable bridge arm energy storage type H-MMC system, which has the advantages of real-time compensation for active power grid impacts, improved system inertia, good submodule consistency, and cost savings through reusable converter bridge arm energy storage.

[0006] The technical solution provided by this invention is as follows:

[0007] A control method for a reusable bridge arm energy storage type H-MMC system, characterized in that the reusable bridge arm energy storage type H-MMC system consists of H-MMC, supercapacitor, and two three-phase power systems;

[0008] The H-MMC system with multiplexed bridge arms consists of six identical bridge arms connected end-to-end to form a hexagonal structure. Each bridge arm comprises M cascaded multiplexed bridge arm energy storage full-bridge submodules and one bridge arm inductor L. b_i These are connected in series, where i represents the i-th bridge arm, and the value of i ranges from 1, 2, 3…6; each multiplexed bridge arm energy storage full-bridge submodule is called an ESSM. _ij Where j represents the j-th multiplexed bridge arm energy storage full-bridge submodule, and the value of j ranges from 1, 2, 3…M; the multiplexed bridge arm energy storage full-bridge submodule consists of four IGBTs S1, S2, S3, and S4 with anti-parallel diodes, and one energy storage inductor L. sc 1 supercapacitor C sc and 1 DC floating capacitor C sm The structure and connection method are as follows: the collectors of S1 and S3 and the DC floating capacitor C sm The positive terminals of S2 and S4 are connected, and the connection point forms the upper node of the multiplexed bridge arm energy storage full-bridge submodule; the emitters of S2 and S4, and the DC floating capacitor C sm The negative electrode and the supercapacitor C sc The negative terminals are connected, and the connection point forms the lower node of the multiplexed bridge arm energy storage full-bridge submodule; supercapacitor C sc The positive electrode and the energy storage inductor L sc Connected; the emitter of S1 and the collector of S2 are connected, and the connection point forms the positive output port of the multiplexed bridge arm energy storage full-bridge submodule; the emitter of S2, the collector of S4, and the energy storage inductor L are connected. sc The other end is connected, and the connection point forms the negative output port of the multiplexed bridge arm energy storage type full bridge submodule;

[0009] In the reusable bridge arm energy storage type H-MMC system, node o1 is the connection point between bridge arm 1 and bridge arm 2; node o2 is the connection point between bridge arm 2 and bridge arm 3; node o3 is the connection point between bridge arm 3 and bridge arm 4; node o4 is the connection point between bridge arm 4 and bridge arm 5; node o5 is the connection point between bridge arm 5 and bridge arm 6; and node o6 is the connection point between bridge arm 6 and bridge arm 1. The six nodes of the reusable bridge arm energy storage type H-MMC system are used to connect two three-phase power systems. Among them, nodes o6, o2, and o4 serve as the primary side three-phase input ports of the reusable bridge arm energy storage type H-MMC system; and nodes o1, o5, and o3 serve as the secondary side three-phase output ports of the reusable bridge arm energy storage type H-MMC system.

[0010] The control strategy of the H-MMC system with multiplexed bridge arm energy storage consists of three parts: main modulation wave control strategy, supercapacitor energy storage control strategy, and modulation wave calculation. The main modulation wave control strategy consists of primary side power command, hierarchical submodule capacitor voltage stabilization and equalization control strategy, and PIR bridge arm current tracking control strategy.

[0011] The main modulation wave control strategy consists of the following steps:

[0012] The main modulation wave u of the bridge arm voltage is obtained based on the primary side power command, the hierarchical submodule capacitor voltage regulation and equalization control strategy, and the PIR bridge arm current tracking control strategy. i_ref ;

[0013] The supercapacitor energy storage control strategy consists of the following steps:

[0014] (1) In the i-th bridge arm and j-th submodule, the rated value u of the supercapacitor voltage. sc_ijref The rated capacitor voltage u of the multiplexed bridge arm energy storage type full bridge submodule is set to... sm_ijref Half of the rated modulation wave m of the supercapacitor voltage _ij Pick:

[0015]

[0016] (2) Set the rated voltage u of the supercapacitor. sc_ijref and actual value u sc_ij Subtracting the two values ​​and feeding the difference into the PI controller, we obtain the supercapacitor voltage modulation correction value m. _ijadd :

[0017]

[0018] Among them, K p and K i These are the proportional and integral coefficients of the PI controller, respectively.

[0019] (3) From the above supercapacitor energy storage control strategies (1)-(2), it can be seen that the modulation wave m of the supercapacitor voltage _ijref :

[0020]

[0021] The modulation wave calculation consists of the following steps:

[0022] (1) will u i_ref Dividing by M yields the modulation wave u of the voltage of the i-th bridge arm and the j-th submodule. ij_ref :

[0023]

[0024] (2) In the i-th bridge arm and j-th submodule, the positive output port modulation signal of the energy storage full-bridge submodule connected to S1 / S2 is u ij_1 / 2ref :

[0025]

[0026] (3) The negative output port modulation signal of the energy storage full-bridge submodule connected to S3 / S4 is u ij_3 / 4ref :

[0027]

[0028] (4) Modulate the signal u ij_1 / 2ref The switching signals of S1 / S2 in the multiplexed bridge arm energy storage full-bridge submodule are obtained by sinusoidal pulse width modulation; the initial phase angle of the sinusoidal pulse width modulation wave is (j-1)*(360 / M)°.

[0029] (5) Modulate the signal u ij_3 / 4ref The switching signals of S3 / S4 in the multiplexed bridge arm energy storage full-bridge submodule are obtained by sinusoidal pulse width modulation; the initial phase angle of the sinusoidal pulse width modulation wave is (j-1)*(360 / M)°.

[0030] The beneficial effects of this invention are: 1) It presents the topology of a reusable bridge arm energy storage type H-MMC system and proposes corresponding control and modulation strategies for this structure. This enables smooth control of the supercapacitor energy storage current and voltage regulation control of the submodule capacitors under high-power scenarios, quickly and effectively solving the active power surge problem in medium and high voltage power systems in the power grid; 2) The structure is simple and cost-effective. It only improves the full-bridge submodules of the original H-MMC system, reuses the converter bridge arm, and connects an energy storage inductor and a supercapacitor in parallel in S4 of each submodule without adding any additional switching devices. Attached Figure Description

[0031] Figure 1 Topology diagram of a reusable bridge arm energy storage type H-MMC system;

[0032] Figure 2 Control block diagram for a reusable bridge arm energy storage type H-MMC system;

[0033] Figure 3 To reuse the capacitor voltage waveform of the full-bridge submodule of the bridge arm;

[0034] Figure 4 The voltage waveform of the full-bridge supercapacitor in the bridge arm is for reuse. Detailed Implementation

[0035] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific examples described herein are merely illustrative and not intended to limit the invention.

[0036] Figure 1This is a topology diagram of a reusable bridge arm energy storage type H-MMC system. The system is characterized by comprising an H-MMC, a supercapacitor, and two three-phase power systems. It consists of six identical bridge arms connected end-to-end to form a hexagonal structure. Each bridge arm comprises M cascaded reusable bridge arm energy storage type full-bridge submodules and one bridge arm inductor L. b_i These are connected in series, where i represents the i-th bridge arm, and the value of i ranges from 1, 2, 3…6; each multiplexed bridge arm energy storage full-bridge submodule is called an ESSM. _ij Where j represents the j-th multiplexed bridge arm energy storage full-bridge submodule, and the value of j ranges from 1, 2, 3…M; the multiplexed bridge arm energy storage full-bridge submodule consists of four IGBTs S1, S2, S3, and S4 with anti-parallel diodes, and one energy storage inductor L. sc 1 supercapacitor C sc and 1 DC floating capacitor C sm The structure and connection method are as follows: the collectors of S1 and S3 and the DC floating capacitor C sm The positive terminals of S2 and S4 are connected, and the connection point forms the upper node of the multiplexed bridge arm energy storage full-bridge submodule; the emitters of S2 and S4, and the DC floating capacitor C sm The negative electrode and the supercapacitor C sc The negative terminals are connected, and the connection point forms the lower node of the multiplexed bridge arm energy storage full-bridge submodule; supercapacitor C sc The positive electrode and the energy storage inductor L sc Connected; the emitter of S1 and the collector of S2 are connected, and the connection point forms the positive output port of the multiplexed bridge arm energy storage full-bridge submodule; the emitter of S2, the collector of S4, and the energy storage inductor L are connected. sc The other end is connected, and the connection point forms the negative output port of the multiplexed bridge arm energy storage type full-bridge submodule; in the multiplexed bridge arm energy storage type H-MMC system, node o1 is the connection point between bridge arm 1 and bridge arm 2; node o2 is the connection point between bridge arm 2 and bridge arm 3; node o3 is the connection point between bridge arm 3 and bridge arm 4; node o4 is the connection point between bridge arm 4 and bridge arm 5; node o5 is the connection point between bridge arm 5 and bridge arm 6; node o6 is the connection point between bridge arm 6 and bridge arm 1; the 6 nodes of the multiplexed bridge arm energy storage type H-MMC system are used to connect two three-phase power systems, wherein nodes o6, o2, and o4 serve as the primary side three-phase input ports of the multiplexed bridge arm energy storage type H-MMC system; nodes o1, o5, and o3 serve as the secondary side three-phase output ports of the multiplexed bridge arm energy storage type H-MMC system.

[0037] In this example, the primary system voltage level is 3.3kV, the secondary power system voltage level is 10kV, and the bridge arm inductor L of the multiplexed bridge arm energy storage type H-MMC system is used. b_i The DC floating capacitor C is 10mH.sm The energy storage inductor L is 20mF. sc For 1mH and supercapacitor C sc The voltage rating is 0.1F. The number of sub-modules M in each bridge arm's multiplexed bridge arm energy storage full-bridge is 6. The rated capacitor voltage u of the j-th sub-module in the i-th bridge arm of the multiplexed bridge arm energy storage full-bridge is... sm_ijref 2500V, K p1 =1、K i1 =20.

[0038] Figure 2 This is the control block diagram of a reusable bridge arm energy storage type H-MMC system. The control strategy consists of three parts: main modulation wave control strategy, supercapacitor energy storage control strategy, and modulation wave calculation. Among them, the main modulation wave control strategy consists of primary side power command, hierarchical submodule capacitor voltage stabilization and equalization control strategy, and PIR bridge arm current tracking control strategy.

[0039] The main modulation wave control strategy consists of the following steps:

[0040] The main modulation wave u of the bridge arm voltage is obtained based on the primary side power command, the hierarchical submodule capacitor voltage regulation and equalization control strategy, and the PIR bridge arm current tracking control strategy. i_ref ;

[0041] The supercapacitor energy storage control strategy consists of the following steps:

[0042] (1) In the i-th bridge arm and j-th submodule, the rated value u of the supercapacitor voltage. sc_ijref The rated capacitor voltage u of the multiplexed bridge arm energy storage type full bridge submodule is set to... sm_ijref Half of the rated modulation wave m of the supercapacitor voltage _ij Pick:

[0043]

[0044] (2) Set the rated voltage u of the supercapacitor. sc_ijref and actual value u sc_ij Subtracting the two values ​​and feeding the difference into the PI controller, we obtain the supercapacitor voltage modulation correction value m. _ijadd :

[0045]

[0046] Among them, K p and K i These are the proportional and integral coefficients of the PI controller, respectively.

[0047] (3) From the above supercapacitor energy storage control strategies (1)-(2), it can be seen that the modulation wave m of the supercapacitor voltage _ijref :

[0048]

[0049] The modulation wave calculation consists of the following steps:

[0050] (1) will u i_ref Dividing by M yields the modulation wave u of the voltage of the i-th bridge arm and the j-th submodule. ij_ref :

[0051]

[0052] (2) In the i-th bridge arm and j-th submodule, the positive output port modulation signal of the energy storage full-bridge submodule connected to S1 / S2 is u ij_1 / 2ref :

[0053]

[0054] (3) The negative output port modulation signal of the energy storage full-bridge submodule connected to S3 / S4 is u ij_3 / 4ref :

[0055]

[0056] (4) Modulate the signal u ij_1 / 2ref The switching signals of S1 / S2 in the multiplexed bridge arm energy storage full-bridge submodule are obtained by sinusoidal pulse width modulation; the initial phase angle of the sinusoidal pulse width modulation wave is (j-1)*(360 / M)°.

[0057] (5) Modulate the signal u ij_3 / 4ref The switching signals of S3 / S4 in the multiplexed bridge arm energy storage full-bridge submodule are obtained by sinusoidal pulse width modulation; the initial phase angle of the sinusoidal pulse width modulation wave is (j-1)*(360 / M)°.

[0058] In the above steps, the primary power command obtains a dynamic value through scheduling, K p1 =1、K i1 =20.

[0059] Figure 3 To reuse the capacitor voltage waveform of submodule 1 in bridge arm 1 of the full-bridge submodule, it can be seen from the 1s to 2s time period that the capacitor voltage balance control effect of the reused full-bridge submodule is good, and the capacitor voltage U of the bridge arm submodule is... 11 It is basically stable around the rated value of 2500V, with a fluctuation range of 4.7%, and only a small fluctuation. This fluctuation range meets the requirements.

[0060] Figure 4To reproduce the supercapacitor voltage waveform of submodule 1 in the multiplexed bridge arm full-bridge submodule, the supercapacitor voltage U of the multiplexed bridge arm full-bridge submodule can be observed within a time period of 1s to 2s. sc_11 The voltage fluctuates around 1250V with a fluctuation range of 4%, which is about 50% of the capacitor voltage of the bridge arm submodule. The supercapacitor can store energy up to half of the submodule's capacitor, which is consistent with the theoretical analysis of this patent.

Claims

1. A control method for a reusable bridge arm energy storage type H-MMC system, characterized in that, The reusable bridge arm energy storage type H-MMC system consists of H-MMC, supercapacitor, and two three-phase power systems; The H-MMC system with multiplexed bridge arms consists of six identical bridge arms connected end-to-end to form a hexagonal structure. Each bridge arm comprises M cascaded multiplexed bridge arm energy storage full-bridge submodules and one bridge arm inductor L. b_i These are connected in series, where i represents the i-th bridge arm, and the value of i ranges from 1, 2, 3…6; each multiplexed bridge arm energy storage full-bridge submodule is called an ESSM. _ij Where j represents the j-th multiplexed bridge arm energy storage full-bridge submodule, and the value of j ranges from 1, 2, 3…M; the multiplexed bridge arm energy storage full-bridge submodule consists of four IGBTs S1, S2, S3, and S4 with anti-parallel diodes, and one energy storage inductor L. sc 1 supercapacitor C sc and 1 DC floating capacitor C sm The structure and connection method are as follows: the collectors of S1 and S3 and the DC floating capacitor C sm The positive terminals of S2 and S4 are connected, and the connection point forms the upper node of the multiplexed bridge arm energy storage full-bridge submodule; the emitters of S2 and S4, and the DC floating capacitor C sm The negative electrode and the supercapacitor C sc The negative terminals are connected, and the connection point forms the lower node of the multiplexed bridge arm energy storage full-bridge submodule; supercapacitor C sc The positive electrode and the energy storage inductor L sc Connected; the emitter of S1 and the collector of S2 are connected, and the connection point forms the positive output port of the multiplexed bridge arm energy storage full-bridge submodule; the emitter of S2, the collector of S4, and the energy storage inductor L are connected. sc The other end is connected, and the connection point forms the negative output port of the multiplexed bridge arm energy storage type full bridge submodule; In the reusable bridge arm energy storage type H-MMC system, node o1 is the connection point between bridge arm 1 and bridge arm 2; node o2 is the connection point between bridge arm 2 and bridge arm 3; node o3 is the connection point between bridge arm 3 and bridge arm 4; node o4 is the connection point between bridge arm 4 and bridge arm 5; node o5 is the connection point between bridge arm 5 and bridge arm 6; and node o6 is the connection point between bridge arm 6 and bridge arm 1. The six nodes of the reusable bridge arm energy storage type H-MMC system are used to connect two three-phase power systems. Among them, nodes o6, o2, and o4 serve as the primary side three-phase input ports of the reusable bridge arm energy storage type H-MMC system; and nodes o1, o5, and o3 serve as the secondary side three-phase output ports of the reusable bridge arm energy storage type H-MMC system. The control strategy of the H-MMC system with multiplexed bridge arm energy storage consists of three parts: main modulation wave control strategy, supercapacitor energy storage control strategy, and modulation wave calculation. The main modulation wave control strategy consists of primary side power command, hierarchical submodule capacitor voltage stabilization and equalization control strategy, and PIR bridge arm current tracking control strategy. The main modulation wave control strategy consists of the following steps: The main modulation wave u of the bridge arm voltage is obtained based on the primary side power command, the hierarchical submodule capacitor voltage regulation and equalization control strategy, and the PIR bridge arm current tracking control strategy. i_ref ; The supercapacitor energy storage control strategy consists of the following steps: (1) In the i-th bridge arm and j-th submodule, the rated value u of the supercapacitor voltage. sc_ijref The rated capacitor voltage u of the multiplexed bridge arm energy storage type full bridge submodule is set to... sm_ijref Half of the rated modulation wave m of the supercapacitor voltage _ij Pick: (2) Set the rated voltage u of the supercapacitor to 100 kJ / kJ. sc_ijref and actual value u sc_ij Subtracting the two values ​​and feeding the difference into the PI controller, we obtain the supercapacitor voltage modulation correction value m. _ijadd : Among them, K p and K i These are the proportional and integral coefficients of the PI controller, respectively. (3) From the above supercapacitor energy storage control strategies (1)-(2), it can be seen that the modulation wave m of the supercapacitor voltage _ijref : The modulation wave calculation consists of the following steps: (1) will u i_ref Dividing by M yields the modulation wave u of the voltage of the i-th bridge arm and the j-th submodule. ij_ref : (2) In the i-th bridge arm and j-th submodule, the positive output port modulation signal of the energy storage full-bridge submodule connected to S1 / S2 is u ij_1 / 2ref : (3) The negative output port modulation signal of the energy storage full-bridge submodule connected to S3 / S4 is u ij_3 / 4ref : (4) Modulate the signal u ij_1 / 2ref The switching signals of S1 / S2 in the multiplexed bridge arm energy storage full-bridge submodule are obtained by sinusoidal pulse width modulation; the initial phase angle of the sinusoidal pulse width modulation wave is (j-1)*(360 / M)°. (5) Modulate the signal u ij_3 / 4ref The switching signals of S3 / S4 in the multiplexed bridge arm energy storage full-bridge submodule are obtained by sinusoidal pulse width modulation; the initial phase angle of the sinusoidal pulse width modulation wave is (j-1)*(360 / M)°.

2. The control method for a reusable bridge arm energy storage type H-MMC system according to claim 1, characterized in that... The primary system voltage level is 3.3kV, and the primary power command is dynamically obtained through dispatch. The secondary power system voltage level is 10kV, and the bridge arm inductor L of the multiplexed bridge arm energy storage type H-MMC system is used. b_i The DC floating capacitor C is 10mH. sm The energy storage inductor is 20mF. sc For 1mH and supercapacitor C sc The voltage rating is 0.1F. The number of sub-modules M in each bridge arm's multiplexed bridge arm energy storage full-bridge is 6. The rated capacitor voltage u of the j-th sub-module in the i-th bridge arm of the multiplexed bridge arm energy storage full-bridge is... sm_ijref 2500V, K p =1、K i =20.

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