Common-mode suppression pulse modulation method for energy storage converters based on ANPC topology

Abstract

This invention discloses a common-mode suppression pulse modulation method for energy storage converters based on ANPC topology. For the ANPC three-level circuit topology used in the converter, a pulse modulation strategy to reduce common-mode voltage is adopted. The pulse modulation unit generates two carriers with a 180° phase shift. This phase shift of the positive and negative half-cycle carriers reduces the common-mode voltage, improving communication reliability in the energy storage system, especially BMS communication reliability. This is because BMS generally uses a CAN communication architecture, and when common-mode interference is high, communication interruptions or anomalies may occur, further leading to safety issues in the energy storage system.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and specifically to a common-mode suppression pulse modulation method for energy storage converters based on ANPC topology. Background Technology

[0002] With the continuous development of electrochemical energy storage technology and industrial and commercial energy storage system technology, the requirements for energy storage safety are becoming increasingly stringent. On the one hand, it is necessary to reduce the cost of energy storage systems and improve economic efficiency; on the other hand, it is necessary to improve the power quality and safety of energy storage systems.

[0003] Currently, commercial and industrial energy storage systems integrate batteries, energy management systems (EMS), battery management systems (BMS), battery management units (BMU), power storage converters (PCS), environmental control systems, and fire protection systems. Communication between EMS, PCS, BMS, and BMU devices in these systems mostly uses CAN or RS-485 communication methods. The power storage converter is the core of the energy conversion and transmission in the energy storage system, realizing the conversion of DC power from the energy storage device to AC power from the grid, as well as the bidirectional energy transmission between the energy storage device and the grid. If the power quality of the power storage converter is poor and common-mode interference is high, it can interfere with the communication system of the energy storage system, affecting its safety. Therefore, effectively improving the grid-connected current quality of the power storage converter and reducing the impact of the system's common-mode voltage on the battery system are key aspects of power storage converter technology.

[0004] Traditional two-level energy storage converters suffer from high switching losses, are difficult to heat dissipate, and cannot be applied to high-power, high-voltage levels.

[0005] The patent document with publication number CN110429629A discloses an energy storage converter and its control method based on NPC three-level topology. It provides a converter based on NPC three-level topology, which reduces switching losses, improves power quality, and also improves voltage and power levels compared to two-level topology. However, the inverter has certain common-mode interference, high IGBT turn-off peak, and there is room for improvement in the efficiency of the converter.

[0006] Patent document CN107196536B discloses a three-level SVPWM method with midpoint balancing and common-mode voltage suppression capabilities, but the calculation process is cumbersome and the algorithm is relatively complex.

[0007] Therefore, current energy storage converters mainly face problems such as high switching losses, low voltage levels, high high-mode voltage, and high turn-off peaks. Summary of the Invention

[0008] 1. The technical problem to be solved:

[0009] To address the aforementioned technical problems, this invention provides a common-mode suppression pulse modulation method for energy storage converters based on ANPC topology, which can reduce common-mode voltage and lower IGBT turn-off spikes.

[0010] 2. Technical Solution:

[0011] A common-mode rejection pulse modulation method for energy storage converters based on ANPC topology is used to pulse modulate the IGBT elements of a three-level converter in an ANPC topology energy storage converter. Each phase arm of the ANPC topology energy storage converter consists of three half-bridge IGBT modules, and each phase arm includes an IGBT element Tn and a diode Dn connected in anti-parallel to Tn, where n = 1 to 6. The method is characterized by the following steps:

[0012] Step 1: The control loop includes a sampling unit, a control unit, and a pulse modulation unit; the control unit generates the modulation wave U. ref With carrier T per The pulse modulation unit modulates the pulse wave U according to the modulation wave U. ref Generate modulated wave U ref13 With modulated wave U ref24 ;where U ref13 For the modulation waves of tubes T1 and T3, U ref24 For the modulation waves of tubes T2 and T4; where, when the modulation wave U ref During the positive half-cycle, U ref13 =U ref U ref24 Greater than carrier T per When the modulated wave U ref During the negative half-cycle, U ref24 =T per +U ref U ref13 Equals 0;

[0013] Step 2: The pulse modulation unit generates two carriers, namely carrier T. per13 T per24 ; where T per13 =T per , will T per T is obtained by phase misalignment of 180° per24 That is, T per13 T per24 The two carrier phases are misaligned by 180°;

[0014] Step 3: Based on the modulation wave U of the positive half-cycle ref13 and carrier T per13 The modulation wave U in the negative half-cycle ref24 and carrier T per24 Generate complementary two-channel PWM 12 Specifically: when the modulating wave Uref13 PWM when the carrier wave is greater than the carrier wave 12 High level, modulation wave U ref13 Less than carrier T per13 PWM 12 When the signal is low, the positive and negative period markers of the modulation wave are P1 and the PN marker of the commutation circuit is P2.

[0015] Step 4: Based on the generated complementary two-channel PWM... 12 The positive and negative period markers P1 and P2 of the commutation circuit generate 6 PWM signals, each corresponding to the pulses of IGBT elements T1, T2, T3, T4, T5, and T6 respectively.

[0016] When the modulation wave U generated by the control unit ref During the positive half-cycle, the pulses T1 and T5 are modulated by the modulation wave U. ref13 and carrier T per13 The comparison yields the following, specifically: if U ref13 ≥T per13 When T1 is high and T5 is low, if U ref13 <T per13 When T1 is low and T5 is high; pulse T2 is always high, and pulses T3, T4, and T6 are always low;

[0017] When the modulation wave U generated by the control unit ref During the negative half-cycle, the pulses T4 and T6 are modulated by the modulation wave U. ref24 and carrier T per24 The comparison yields the following, specifically: if U ref24 ≥T per24 When T4 is high and T6 is low; if u ref24 <T per24 When T4 is low and T6 is high; the pulse T3 is always high, and the pulses T2, T1, and T5 are always low.

[0018] Step 5: Perform narrow pulse suppression on all 6 PWM signals generated in Step 4; that is, if it is a narrow pulse, do not output the narrow pulse.

[0019] Step 6: Insert the dead time into the output pulse generated in Step 5 to obtain the drive pulses for IGBT elements T1, T2, T3, T4, T5, and T6.

[0020] Furthermore, the three-level converter of the ANPC topology specifically comprises: IGBT module 1 includes switching elements T1 and T5, and diodes D1 and D5, wherein T1 and T5 are connected in reverse parallel to D1 and D5 respectively; IGBT module 2 includes switching elements T2 and T3, and diodes D2 and D3, wherein T2 and T3 are connected in reverse parallel to D2 and D3 respectively; IGBT module 3 includes switching elements T4 and T6, and diodes D4 and D6, wherein T4 and T6 are connected in reverse parallel to D4 and D6 respectively; the pulse modulation unit of the energy storage converter of the ANPC topology receives the control signal from the control loop and generates 6 drive pulse signals to the drive circuit, and the drive circuit controls the on / off of the corresponding IGBT module to realize the AC / DC conversion of the energy storage converter.

[0021] 3. Beneficial effects:

[0022] (1) This invention provides a common-mode suppression pulse modulation method for energy storage converters based on ANPC topology. The converter adopts an ANPC three-level circuit topology to solve the problem of excessively high turn-off voltage spikes in NPC three-level converters. Using the ANPC topology can reduce turn-off voltage spikes, that is, increase the DC voltage range of the energy storage converter. For industrial and commercial energy storage systems at a voltage level of 1000V, the DC voltage range can reach 600V to 950V. For IGBTs with a voltage level of 650V, if the turn-off spike is large, it can easily cause IGBT overvoltage damage. The ANPC three-level topology circuit uses IGBT modules to replace the original clamping diodes on the basis of NPC three-level, thereby eliminating the long-loop commutation of the three-level inverter and reducing the turn-off spike.

[0023] (2) The present invention provides a common-mode suppression pulse modulation method for energy storage converter based on ANPC topology, which adopts a pulse modulation strategy to reduce common-mode voltage. The pulse modulation unit generates two carriers with a phase shift of 180°. The common-mode voltage is reduced by the phase shift of the positive and negative half-cycle carriers, which improves the communication reliability in the energy storage system, especially the BMS communication reliability. This is because BMS generally adopts CAN communication architecture. When the common-mode interference is large, communication interruption or communication abnormality will occur, which will further lead to the safety problem of the energy storage system.

[0024] In summary, this invention can improve the DC-side voltage range of the energy storage system, enhance the safety of the energy storage converter under high DC-side voltage, reduce the common-mode voltage, and improve the communication reliability and energy storage performance safety of the energy storage system. Attached Figure Description

[0025] Figure 1 This is a block diagram of the ANPC three-level topology energy storage converter involved in the present invention;

[0026] Figure 2The circuit diagram of the ANPC three-level circuit involved in this invention is shown below;

[0027] Figure 3 Two carrier waveforms generated by the pulse modulation unit of this invention;

[0028] Figure 4 This is an overall flowchart of pulse modulation of ANPC in this invention;

[0029] Figure 5 This is a pulse modulation diagram of the three-phase bridge arm controlled by the three-phase carrier of the three-phase converter of the present invention;

[0030] Figure 6 This is a timing diagram of the final output pulse waveform of the present invention. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings.

[0032] As attached Figure 1 As shown, the system connection diagram of the energy storage converter based on the ANPC three-level topology involved in this invention mainly includes a control loop, an LC filter circuit, an ANPC three-level inverter circuit, a DC-side capacitor, a DC charging loop, and an energy storage battery.

[0033] The control loop of the energy storage converter consists of a sampling unit, a digital control unit, and a pulse modulation unit. The control loop is connected to the fire protection system, BMS system, EMS system, and environmental control system within the energy storage system. The LC filter circuit is connected to the ANPC three-level inverter circuit, which is connected to the DC-side capacitor. The DC-side capacitor is connected to the DC charging circuit, which is connected to the energy storage battery. The LC filter circuit filters out the harmonics of the ANPC three-level converter's output current, significantly reducing the harmonic content. The ANPC three-level converter performs AC / DC conversion, converting AC to DC to charge the energy storage battery and converting DC to AC to discharge the energy storage current. The DC charging circuit pre-charges the energy storage battery and the DC-side capacitor, completing the pre-charging process of the ANPC energy storage converter's DC-side capacitor.

[0034] The specific circuit of the ANPC three-level inverter circuit is as follows: Figure 2 As shown, it is based on the NPC three-level circuit, replacing the clamping diode with IGBT. That is, it is composed of IGBT elements T1, T2, T3, T4, T5, T6 and anti-parallel diodes D1, D2, D3, D4, D5, D6. The commutation loops T5 and T6 are added. By using a specific pulse modulation method, the long loop commutation of the converter can be avoided and the turn-off spike can be reduced.

[0035] Therefore, the common-mode voltage of a three-level converter is the potential difference between the three-phase output neutral point and the DC bus neutral point (reference ground), and its common-mode voltage is:

[0036]

[0037] In the above formula: U om Common-mode voltage; S a S b Sc represents the switching state of the three-phase bridge arms, with three switching states: 1, 0, and -1. U dc This is the DC bus voltage.

[0038] As can be seen from the above formula, the common-mode voltage is related to the switching state of the three-phase bridge arm and the DC bus voltage. The switching state of the three-phase bridge arm of the energy storage converter is determined by the pulse modulation method and the switching frequency.

[0039] To improve the DC voltage range and reduce the common-mode voltage of the three-level energy storage converter, the technical solution adopted in this invention is as follows: a three-level carrier phase-shifted ANPC short-loop commutator pulse modulation method is used to suppress the common-mode voltage within... Within this range, the shutdown spikes are reduced, the DC voltage range of the energy storage converter is increased, and the current output quality is not affected.

[0040] A common-mode rejection pulse modulation method based on ANPC topology is used to pulse modulate the IGBT elements of the three-level converter in the ANPC topology energy storage converter. Each phase arm of the ANPC topology energy storage converter consists of three half-bridge IGBT modules, and each phase arm includes an IGBT element Tn and a diode Dn connected in anti-parallel to Tn, where n = 1 to 6. (See attached diagram.) Figure 4 As shown, it includes the following steps:

[0041] Step 1: The control loop includes a sampling unit, a control unit, and a pulse modulation unit; the control unit generates the modulation wave U. ref With carrier T per The pulse modulation unit modulates the pulse wave U according to the modulation wave U. ref Generate modulated wave U ref13 With modulated wave U ref24 ;where U ref13 For the modulation waves of tubes T1 and T3, U ref24 For the modulation waves of tubes T2 and T4; where, when the modulation wave U ref During the positive half-cycle, U ref13 =U ref U ref24 Greater than carrier T per When the modulated wave U ref During the negative half-cycle, U ref24 =Tper +U ref U ref13 Equals 0;

[0042] Step 2: The pulse modulation unit generates two carriers, namely carrier T. per13 T per24 ; where T per13 =T per , will T per T is obtained by phase misalignment of 180° per24 That is, T per13 T per24 The two carrier phases are misaligned by 180°;

[0043] As attached Figure 3 As shown, Figure 3 In the diagram, 1 and 5 represent the corresponding positive half-cycle carrier waves; 3 and 6 represent the corresponding negative half-cycle carrier waves; 2 represents the positive half-cycle modulated wave; and 4 represents the negative half-cycle modulated wave.

[0044] Step 3: Based on the modulation wave U of the positive half-cycle ref13 and carrier T per13 The modulation wave U in the negative half-cycle ref24 and carrier T per24 Generate complementary two-channel PWM 12 Specifically: when the modulating wave U ref13 PWM when the carrier wave is greater than the carrier wave 12 High level, modulation wave U ref13 Less than carrier T per13 PWM 12 When the signal is low, the positive and negative period markers of the modulation wave are P1 and the PN marker of the commutation circuit is P2.

[0045] Step 4: Based on the generated complementary two-channel PWM... 12 The positive and negative period markers P1 and P2 of the commutation circuit generate 6 PWM signals, each corresponding to the pulses of IGBT elements T1, T2, T3, T4, T5, and T6 respectively.

[0046] When the modulation wave U generated by the control unit ref During the positive half-cycle, the pulses T1 and T5 are modulated by the modulation wave U. ref13 and carrier T per13 The comparison yields the following, specifically: if U ref13 ≥T per13 When T1 is high and T5 is low, if U ref13 <T per13 When T1 is low and T5 is high; pulse T2 is always high, and pulses T3, T4, and T6 are always low;

[0047] When the modulation wave U generated by the control unitref During the negative half-cycle, the pulses T4 and T6 are modulated by the modulation wave U. ref24 and carrier T per24 The comparison yields the following, specifically: if U ref24 ≥T per24 When T4 is high and T6 is low; if U ref24 <T per24 When T4 is low and T6 is high; the pulse T3 is always high, and the pulses T2, T1, and T5 are always low.

[0048] Step 5: Perform narrow pulse suppression on all 6 PWM signals generated in Step 4; that is, if it is a narrow pulse, do not output the narrow pulse.

[0049] Step 6: Insert the dead time into the output pulse generated in Step 5 to obtain the drive pulses for IGBT elements T1, T2, T3, T4, T5, and T6.

[0050] Furthermore, the three-level converter of the ANPC topology specifically comprises: IGBT module 1 includes switching elements T1 and T5, and diodes D1 and D5, wherein T1 and T5 are connected in reverse parallel to D1 and D5 respectively; IGBT module 2 includes switching elements T2 and T3, and diodes D2 and D3, wherein T2 and T3 are connected in reverse parallel to D2 and D3 respectively; IGBT module 3 includes switching elements T4 and T6, and diodes D4 and D6, wherein T4 and T6 are connected in reverse parallel to D4 and D6 respectively; the pulse modulation unit of the energy storage converter of the ANPC topology receives the control signal from the control loop and generates 6 drive pulse signals to the drive circuit, and the drive circuit controls the on / off of the corresponding IGBT module to realize the AC / DC conversion of the energy storage converter.

[0051] like Figure 5 As shown, the energy storage converter is a three-phase converter with a positive half-cycle modulation wave U. ref13 Negative half-cycle modulated wave U ref24 The positive and negative half-cycle carriers are out of phase T per13 T per24 It can control the phase shift of the three-phase bridge arm's high and low level changes in each switching cycle, thereby obtaining the phase-shifted switching state S of the three-phase bridge arm. a S b Sc, reduce common-mode voltage U om The sine wave in the diagram is a three-phase modulated wave of phases A, B, and C; the triangular wave is two carrier waves out of phase by 180°; S a S b Sc represents the equivalent modulation output switching state.

[0052] Figure 6 The timing diagram of the final output pulse waveform of the present invention is shown in the figure. In Uref During the positive half-cycle, T2 is turned on, and T1 and T5 are pulse-modulated, causing current to commutate from T1 and T5, thus avoiding commutation between T1 and D6 in the NPC three-level converter. ref During the negative half-cycle, T3 is turned on, and T4 and T6 are pulse-modulated, with current commutated from T4 and T6. This avoids commutation between T4 and D5 in the NPC three-level converter, thus avoiding long-loop commutation, reducing turn-off spikes, and improving the reliability and safety of the energy storage converter when the DC side voltage is high.

[0053] Although the present invention has been disclosed above with reference to preferred embodiments, these are not intended to limit the invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims of this application.

Claims

1. A common-mode rejection pulse modulation method for an energy storage converter based on ANPC topology, used for pulse modulation of the IGBT elements of a three-level converter in an ANPC topology energy storage converter; each phase arm of the ANPC topology energy storage converter consists of three half-bridge IGBT modules, each phase arm including an IGBT element Tn and a diode Dn connected in anti-parallel to Tn, where n=1~6; characterized in that: Includes the following steps: Step 1: The control loop includes a sampling unit, a control unit, and a pulse modulation unit; the control unit generates the modulated wave. With carrier ; The pulse modulation unit modulates the pulse wave according to the modulation wave. Generate modulated wave With modulated wave ;in The modulation waves of tubes T1 and T3, The modulation waves of tubes T2 and T4; where, when the modulation wave During the positive half-cycle, , Greater than carrier When the modulated wave During the negative half-cycle , Equal to 0; Step 2: The pulse modulation unit generates two carrier waves, namely carrier waves. , ;in ,Will A 180° phase shift is obtained ;Right now , The two carrier phases are misaligned by 180°; Step 3: Based on the modulation wave of the positive half-cycle and carrier Modulated wave of negative half-cycle and carrier Generate complementary two-channel PWM 12 Specifically, when the modulated wave PWM when the carrier wave is greater than the carrier wave 12 High level, modulated wave Less than carrier PWM 12 When the signal is low, the positive and negative period markers of the modulation wave are P1 and the PN marker of the commutation circuit is P2. Step 4: Based on the generated complementary paths The positive and negative period flag P1 of the modulation wave and the PN flag P2 of the commutation circuit generate 6 PWM signals, each PWM signal corresponding to the pulses of IGBT elements T1, T2, T3, T4, T5, and T6 respectively; When the modulated wave generated by the control unit During the positive half-cycle, the pulses T1 and T5 are modulated by the wave. and carrier The comparison yields the following, specifically: if When T1 is high and T5 is low, if When T1 is low and T5 is high; pulse T2 is always high, and pulses T3, T4, and T6 are always low. When the modulated wave generated by the control unit During the negative half-cycle, pulses T4 and T6 are modulated by the wave. and carrier The comparison yields the following, specifically: if When T4 is high and T6 is low; if When T4 is low and T6 is high; the pulse T3 is always high, and the pulses T2, T1, and T5 are always low. Step 5: Perform narrow pulse suppression on all 6 PWM signals generated in Step 4; that is, if it is a narrow pulse, do not output the narrow pulse. Step 6: Insert the dead time into the output pulse generated in Step 5 to obtain the drive pulses for IGBT elements T1, T2, T3, T4, T5, and T6; The three-level converter of the ANPC topology is specifically as follows: IGBT module 1 includes switching elements T1 and T5, and diodes D1 and D5, wherein T1 and T5 are connected in anti-parallel to D1 and D5 respectively; IGBT module 2 includes switching elements T2 and T3, and diodes D2 and D3, wherein T2 and T3 are connected in anti-parallel to D2 and D3 respectively; IGBT module 3 includes switching elements T4 and T6, and diodes D4 and D6, wherein T4 and T6 are connected in anti-parallel to D4 and D6 respectively; the pulse modulation unit of the energy storage converter of the ANPC topology receives the control signal from the control loop and generates 6 drive pulse signals to the drive circuit, and the drive circuit controls the on / off of the corresponding IGBT module to realize the AC-DC conversion of the energy storage converter.

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