Energy-saving and parallel superimposed connection method of three-phase CSR rectifier circuit

Abstract

The application discloses a three-phase CSR rectifier circuit energy-saving and parallel superposition wiring method, comprising two windings of a power supply distribution transformer low-voltage side output, two windings respectively supply power to two groups of CSR half-bridge rectifier circuits, two windings are equal in voltage, and corresponding phases are the same in phase. Each winding is respectively provided with a group of CSR half-bridge arm loops, two groups of CSR half-bridge arm loops work in respective working time, the working time corresponding angle interval is 60 DEG, an alternating working mode is formed and time is complementary, and full-bridge CSR high-frequency rectification function is completed. The application provides a three-phase CSR rectifier circuit energy-saving and parallel superposition wiring method which reduces switch tubes, reduces power consumption, is high in voltage resistance, large in power factor, small in harmonic, and large in power.

Description

Technical Field

[0001] This invention relates to the field of CSR rectifier circuit technology, and in particular to a wiring method for energy saving and parallel superposition of three-phase CSR rectifier circuits. Background Technology

[0002] CSR rectifier circuits are high-frequency PWM (Pulse Width Modulation) current source step-down rectifier power supply circuits. High-power rectifier circuits typically use a three-phase input power supply, such as... Figure 1 The diagram shows the topology of a three-phase six-switch CSR rectifier circuit used in the prior art.

[0003] Existing CSR rectifier circuits feature high power factor and high output power control accuracy through PFC function. Currently, CSR rectifier circuits achieve high-frequency operation through high-power switching transistors, resulting in low harmonics due to the high operating frequency of the circuit.

[0004] In existing CSR rectifier circuits, the switching of the transistors is controlled by a control loop. This control loop adjusts the pulse width (PWM) based on the load requirements. The pulse width is determined by modulating a triangular carrier wave with a sine wave. Since the power supply is sinusoidal, a sine wave is used as the modulation wave to improve the power factor, causing the current and voltage to change synchronously. This is also called SPWM high-frequency rectifier power supply, where S represents a sine wave, and will be referred to as PWM below.

[0005] Currently, high-power rectifier control is accomplished using dedicated DSP digital signal controllers, based on the same principle as triangular wave modulation. The losses in the rectifier circuit mainly occur during the switching process of the switching transistors and during saturation conduction; therefore, reducing the number of operating switching transistors is the primary objective of this invention.

[0006] In addition, in many cases, CSR rectifier circuits need to operate under high voltage and high current conditions. Currently, the manufacturing technology of transistors is not fast enough to produce high voltage and high current switching transistors. To achieve a high power factor, low harmonics, and high power, the circuit operating frequency must be greater than 20 kHz. Therefore, multiple CSR rectifier circuits must be connected in parallel to achieve this. Summary of the Invention

[0007] In view of this, the present invention provides a wiring method for energy saving and parallel superposition of a three-phase CSR rectifier circuit that reduces the number of switching transistors, lowers power consumption, has high withstand voltage, large power factor, low harmonics, and increases power.

[0008] To achieve the objectives of this invention, the following technical solutions can be adopted:

[0009] A wiring method for energy saving and parallel superposition of three-phase CSR rectifier circuits, wherein the power supply distribution transformer outputs two windings on the low-voltage side, and the two windings supply power to two sets of CSR half-bridge rectifier circuits respectively, with the voltage of the two windings being equal and the corresponding phases being the same.

[0010] Each winding carries a set of CSR half-bridge arm circuits. The two sets of CSR half-bridge arm circuits work during their respective working times, with the working time corresponding to an angle range of 60°, forming an alternating working mode and complementing each other in time, thus completing the high-frequency rectification function of the full-bridge CSR.

[0011] The two sets of CSR half-bridge arm circuits can be connected in parallel and superimposed to form multiple sets of CSR half-bridge arm circuits.

[0012] The beneficial effects of this invention are as follows: This invention reduces circuit losses by decreasing the number of operating switching transistors in the CSR rectifier circuit. Specifically, two windings are output from the low-voltage side of the power distribution transformer. The two windings have equal voltages, are electrically disconnected, and each carries a CSR half-bridge arm circuit. The two circuits operate during their respective operating times, with corresponding angles of 60°, forming an alternating mode with complementary operating times. From the primary input of the transformer, the current sinusoidal wave remains undistorted, achieving a perfect "full-bridge" CSR high-frequency rectification function. Furthermore, the two windings on the low-voltage side of the distribution transformer, each carrying a CSR half-bridge arm circuit, with each half-bridge carrying an energy storage inductor. The circuit operation is symmetrical, allowing for effective parallel superposition and increasing output power. Attached Figure Description

[0013] Figure 1 This is a prior art three-phase CSR rectifier circuit topology diagram for the energy-saving and parallel superposition wiring method of the three-phase CSR rectifier circuit according to an embodiment of the present invention;

[0014] Figure 2 The waveform diagram of the three-phase CSR rectifier circuit is shown in the embodiment of the present invention for the energy-saving and parallel superposition wiring method of the three-phase CSR rectifier circuit.

[0015] Figure 3 The diagram shows a three-phase CSR rectifier circuit for energy saving and parallel superposition wiring method in an embodiment of the present invention. Detailed Implementation

[0016] The invention will now be described in further detail with reference to the accompanying drawings and embodiments thereof.

[0017] This invention proposes a wiring method for energy saving and parallel superposition of three-phase CSR rectifier circuits.

[0018] See Figure 1The characteristic of existing three-phase CSR rectifier circuits is that commutation occurs between the upper and lower bridge arm switches of adjacent phases. Figure 1 This is the topology diagram of a CSR rectifier circuit. V1, V2, and V3 are the upper bridge arm switching transistors of phases A, B, and C, respectively; D1, D2, and D3 are the upper bridge arm diodes of phases A, B, and C, respectively; V4, V5, and V6 are the lower bridge arm switching transistors of phases A, B, and C, respectively; D4, D5, and D6 are the lower bridge arm diodes of phases A, B, and C, respectively; L4 is the energy storage inductor; and D7 is the freewheeling diode.

[0019] The existing three-phase CSR rectifier circuit is powered by one winding of a distribution transformer. At any given moment during the operation of the CSR rectifier circuit, only one of the three switches in the upper arm and the three switches in the lower arm is conducting, forming a closed-loop rectification circuit between phases. For example, if switch V1 in the upper arm is conducting, then either switch V5 or V6 in the lower arm is conducting, thus creating a current path. The operation of the other switches follows the same principle.

[0020] See Figure 2 ,Should Figure 2 The diagram shows the three-phase sine wave waveforms of a three-phase CSR rectifier circuit. Figure 2 In the diagram, Ua, Ub, and Uc represent the three-phase voltages A, B, and C as a function of time (or angle). Figure 2 Choose any point D on the time axis. At this time, the corresponding voltage values ​​of points A, B, and C are points F, G, and E, respectively.

[0021] According to the operating principle of CSR circuits, the operating voltage at this point should be Uab (segment FG represents the magnitude of Uab) or Ubc (segment EG represents the magnitude of Ubc). Taking voltage Uab as an example, this... Figure 1 The corresponding switching transistors V1 and V5 are turned on, and the current i follows the... Figure 1 The dashed line shows the flow from phase A through V1, D1, L4, load RL, and V5, D5 before returning to phase B. In this process, the main components generating losses in the CSR circuit are V1, D1, V5, D5, two switching transistors, and two diodes. Similarly, it can be analyzed that each conduction process generates losses from two switching transistors and two diodes, with the switching transistors experiencing significantly greater losses than the diodes. Reducing the number of switching transistors is the primary objective of this invention.

[0022] This invention reduces loop losses by reducing the number of operating switching transistors in existing CSR rectifier circuits.

[0023] The specific method involves two windings on the low-voltage side of the power distribution transformer. The two windings have equal voltages, are not electrically connected, and each carries a CSR half-bridge arm circuit. The two circuits operate at their respective operating times, with the operating time corresponding to an angle of 60°, forming an alternating mode and complementary operating times. From the primary side input of the transformer, the current sine wave remains undistorted, thus achieving a perfect "full-bridge" CSR high-frequency rectification function.

[0024] See Figure 3 Distribution transformer 1 has a primary side connected to the high voltage of the power grid, and a secondary side outputting two windings, namely the first winding and the second winding. The voltages of these two windings are equal, and the corresponding phases are the same. Each winding drives its own CSR half-bridge circuit.

[0025] like Figure 3 In the first winding, the first CSR half-bridge circuit 2, the distribution transformer 1 and the first CSR half-bridge circuit 2 together are called the upper half region; the second winding, the second CSR half-bridge circuit 3, the distribution transformer 1 and the second CSR half-bridge circuit 3 together are called the lower half region.

[0026] The CSR half-bridge circuit described in this invention differs from the traditional CSR full-bridge circuit. Existing CSR full-bridge circuits, such as... Figure 1 Each of the upper and lower bridge arms has three symmetrical switching transistors and diodes.

[0027] The CSR half-bridge circuit described in this invention is as follows: Figure 3 , Figure 3 The dashed box 2 shows the first CSR half-bridge circuit 2 in the upper half region.

[0028] The first CSR half-bridge circuit 2 eliminates the three switching transistors of the lower bridge arm of the existing circuit. The upper half of the first CSR half-bridge circuit 2 is specifically composed of switching transistors V11, V12, and V13 and diodes D11, D12, and D13, and the lower half-bridge is composed of diodes D14, D15, and D16.

[0029] like Figure 3 The second CSR half-bridge circuit 3 in the lower half region eliminates the three switching transistors of the upper bridge arm of the existing circuit. Specifically, the upper half-bridge is composed of diodes D21, D22, and D23, and the lower half-bridge is composed of switching transistors V24, V25, and V26, as well as diodes D24, D25, and D26.

[0030] The angles corresponding to the upper and lower working periods are strictly defined. The upper working range is 0°~60°, 120°~180°, 240°~300°…; the lower working range is 60°~120°, 180°~240°, 300°~360°….

[0031] Specific work processes combined Figure 2 , Figure 3 analyze, Figure 2 The voltage operating range is set between 0° and 60°. During this period, the upper half of the first winding of distribution transformer 1 operates under the CSR half-bridge circuit 2. In the lower half of the second winding of the transformer, all switches in the CSR circuit 3 are in the off state; therefore, the lower half of the circuit does not operate, meaning V24, V25, and V26 (including V224, V225, and V226) are all off. (Optional) Figure 2 At point D in the circuit, the CSR circuit operates at voltage Uab or Ubc. Assuming voltage Uab is active, the operating process is as follows: V11 turns on, and current flows from phase A through D11, V11, L14, load RL, and D15 back to phase B. Figure 3 The direction of current i in the upper half-bridge CSR circuit 2 is shown. The voltage values ​​corresponding to points A, B, and C at point D are points F, G, and E, respectively. It can be seen that the voltage of phase B is lowest in the 0°–60° range. Although the lower bridge arm has three diodes D14, D15, and D16, the current can only flow back from the phase with the lowest potential, B. Therefore, the current in phase A can only flow back from phase B (D15) and cannot flow back from phase C. Thus, during the operation of Uab, the main components causing losses in the CSR circuit are D11, V11, D15, one switching transistor, and two diodes. This process reduces the loss of one switching transistor compared to traditional CSR operation.

[0032] Assuming the voltage Ubc is operating near point D, V13 is turned on, and current flows from phase C through D13, V13, L14, load RL, and D15 back to phase B. Since phase B has the lowest potential in the 0° to 60° range, the current in phase C can only flow back through diode D15 in phase B and cannot flow back from phase A.

[0033] Therefore, during UBC operation, the components that generate losses in the CSR circuit are D13, V13, D15, one switching transistor, and two diodes. This process also reduces the loss of one switching transistor compared to traditional CSR operation.

[0034] like Figure 2 When the voltage operates within the range of 60° to 120°, the second winding of distribution transformer 1 and the second CSR half-bridge circuit 3 in the lower half zone are working. All the switching transistors in the upper half zone CSR half-bridge circuit 2 of the first winding of distribution transformer 1 are cut off, that is, V11, V12, V13 (including V121, V122, V123) are all cut off, and the upper half zone is not working during this period.

[0035] exist Figure 2Choose any point H. At this point, the voltage values ​​of phases A, B, and C correspond to points K, J, and I, respectively. Although there are three diodes D21, D22, and D23 in the upper bridge arm, it can be seen that the potential of phase A is the highest in the 60°–120° range. Therefore, the current can only flow out from diode D21 in phase A, and cannot flow out from diodes D22 and D23 in phases B and C. The characteristic of the CSR circuit at this point is that the operating voltage can only be Uab or Uac. Taking Uab voltage operation as an example, with V25 turned on, the current flows back from phase B through V25. The current flows through devices D21, load RL, L24, V25, and back to phase B via D25. In this process, the devices that generate losses in the CSR half-bridge circuit are D21, V25, D25, one switching transistor, and two diodes, which reduces the loss of one switching transistor compared to the traditional CSR rectifier circuit. The same analysis shows the same loss situation when operating at voltage Uac.

[0036] Similarly, since the C-phase potential is lowest in the 120°–180° range, the CSR circuit can only operate under voltages Uac and Ubc at this time, and the currents in phases A and B can only flow back from phase C. Analyzing voltages Uac and Ubc in the same way, the devices that generate losses in the CSR half-bridge circuit during their operation are a single switching transistor and two diodes.

[0037] The upper and lower half-bridge circuits switch every 60°, and the control method is arranged according to the above principle, thus successfully completing the CSR symmetrical rectification work. The original CSR full-bridge rectifier circuit had losses from two switching transistors and two diodes; this invention's CSR half-bridge rectifier saves the loss of one switching transistor.

[0038] The switching transistor's losses consist of two parts: switching process losses and saturation conduction voltage drop losses. The saturation conduction voltage drop is approximately 3 volts. If the circuit has a current of 50 amps, the switching transistor's saturation conduction loss is 150 watts, meaning the switching process losses are more than three times the saturation conduction losses. In contrast, the diode's voltage drop is less than 1 volt, and its losses are less than 50 watts with a 50 amp current. Therefore, the CSR half-bridge rectifier circuit of this invention saves one switching transistor, effectively reducing circuit losses by more than 30%.

[0039] With current transistor manufacturing technology, the operating frequency of high-voltage, high-power switching transistors cannot be made too high. To improve the power factor, reduce harmonics, and increase power output of CSR rectifier circuits, multiple CSR rectifier circuits need to be connected in parallel and superimposed.

[0040] Existing CSR full-bridge rectifier circuits can only have one energy storage inductor in the bridge output circuit, such as Figure 1 L4 in the circuit causes asymmetry in the output circuit. Figure 2 Medium voltage circuits can be connected in parallel and superimposed during the first half of a sine wave, but not during the second half, which means that multiple CSR rectifier circuits cannot be connected in parallel and superimposed.

[0041] In this invention, the low-voltage side of the distribution transformer 1 has two windings with equal voltages, no electrical connection, and each winding carries a set of CSR half-bridge arm circuits, forming upper and lower half-zones. Each half-bridge in the upper and lower half-zones carries an energy storage inductor, so the upper and lower half-cycles of the voltage sine wave are balanced, and the two half-zones are combined to complete the fully symmetrical CSR rectification work.

[0042] like Figure 3 The two half-bridges in the upper half are equipped with inductors L14 and L124, respectively; the two half-bridges in the lower half are equipped with inductors L24 and L224, respectively. The circuit operation is symmetrical and can be well implemented in parallel superposition.

[0043] like Figure 3 The upper half-bridge circuit 2 includes a first parallel superimposed loop 4, which is the second group of CSR half-bridge arm loops in the upper half-bridge. Specifically, it consists of switching transistors V121, V122, and V123, and diodes D121, D122, and D123. Inductor L124 is the energy storage element of the first parallel superimposed loop 4 half-bridge. The current from each switching transistor in the first parallel superimposed loop 4 flows through the load, performs work, and then returns to the power supply via diodes D14, D15, and D16 in the first CSR half-bridge circuit 2.

[0044] See Figure 3 The second CSR half-bridge circuit 3 includes a second parallel superimposed circuit 5, which is the second group of CSR half-bridge arm circuits in the lower half region. Specifically, it consists of switching transistors V224, V225, and V226, and diodes D224, D225, and D226. Inductor L224 is the energy storage element of the second parallel superimposed circuit 5 half-bridge.

[0045] In the second parallel superimposed circuit 5, the current of each switch transistor flows through the load and then through diodes D21, D22, and D23 in the second CSR half-bridge circuit 3 back to the power supply. Among them, D14, D15, and D16 are common diodes for the return current of each group in the upper half region, and D21, D22, and D23 are common diodes for the output current of each group in the lower half region.

[0046] Figure 3 Only two parallel superimposed circuits are shown in the diagram. In practice, multiple parallel superimposed circuits can be used, with the specific number determined by the load requirements. The control phases of subsequent circuits are phase-shifted relative to the first circuit. Assume there are N CSR rectifier circuits connected in parallel, each using carrier triangular wave phase-shift control. The angle between the N triangular waves within the triangular wave period is... All N CSR rectifier circuits are modulated with the same sine wave. The parallel superposition control technology is based on the same principle as the existing mature voltage source VSR rectifier circuit parallel superposition technology, and will not be elaborated here.

[0047] This invention reduces circuit losses by decreasing the number of operating switches in a CSR rectifier circuit. Specifically, two windings are introduced on the low-voltage side of the power distribution transformer. These two windings have equal voltages, are electrically disconnected, and each drives a CSR half-bridge arm circuit, forming upper and lower sets of circuits. Each CSR half-bridge arm circuit reduces three switches in the upper arm of one set and three switches in the lower arm of the other set. The two circuits operate during their respective operating times, corresponding to an angle range of 60°. This alternating and complementary operation ensures the current remains a sinusoidal wave without distortion, thus completing the high-frequency rectification function of the full-bridge CSR. See [link / reference]. Figure 3 The dashed boxes 2 and 3 represent the upper and lower sets of CSR half-bridge arm circuits, respectively. When the two half-bridge circuits operate independently, one fewer switching transistor is required compared to the original CSR full-bridge circuit, thus reducing circuit losses. Furthermore, the distribution transformer has two windings on the low-voltage side, each driving one set of CSR half-bridge arm circuits. Both the upper and lower half-bridges are equipped with an energy storage inductor. This symmetrical circuit operation allows for effective parallel superposition, thereby increasing output power.

Claims

1. A wiring method for energy saving and parallel superposition of three-phase CSR rectifier circuits, comprising: Two sets of half-bridge arms CSR (2) and (3) form a complete CSR rectifier circuit. Each set of CSR half-bridge arm circuits includes three-phase half-bridge arms, and each phase bridge arm has one switching transistor (V11, V12, V13); (V24, V23, V26). Its features are: the two sets of half-bridge arms CSR (2, 3) are respectively connected to the two low-voltage windings of the transformer, and the voltages of the two low-voltage windings are equal and the phases are the same; The two sets of CSR half-bridge arm circuits work at their respective working times, and the working time corresponds to the power waveform angle range of 60°, forming an alternating working mode and time complementing each other. The two sets of circuits work to form the complete function of CSR high-frequency rectification, so that the sine wave on the primary side of the distribution transformer (1) is not distorted. The two sets of CSR half-bridge arms include a first CSR half-bridge circuit and a second CSR half-bridge circuit. The first CSR half-bridge circuit includes three bridge arms. The upper arm of each bridge consists of a diode and a switching transistor connected in series. The anode of the diode is connected to the AC input terminal, the cathode of the diode is connected to the collector of the switching transistor, and the emitter of the switching transistor is connected to the positive output of the rectifier bridge. The lower arm of each of the three bridge arms is a diode. The anode of the diode is connected to the negative output of the bridge arm, and the cathode is connected to the AC input terminal. The second CSR half-bridge circuit includes three bridge arms. The lower arm of each bridge consists of a diode and a switching transistor connected in series. The cathode of the diode is connected to the AC input terminal, the anode of the diode is connected to the collector of the switching transistor, and the emitter of the switching transistor is connected to the negative output of the rectifier bridge. The upper arm of each of the three bridge arms is a diode. The cathode of the diode is connected to the positive output of the bridge arm, and the anode is connected to the AC input terminal.

2. The wiring method for energy saving and parallel superposition of three-phase CSR rectifier circuits according to claim 1, characterized in that: The CSR half-bridge arm circuit has multiple parallel superimposed circuits after the filter inductor. The first winding upper half region CSR half-bridge arm circuit 2 and the first parallel superimposed circuit 4 are connected in parallel after inductors L11-L13; the second CSR half-bridge arm circuit 3 and the second parallel superimposed circuit 5 are connected in parallel after inductors L21-L23.

3. A three-phase CSR rectifier circuit, characterized in that: It includes two CSR half-bridge arm circuits. The power distribution transformer outputs two windings on the low-voltage side, and the two windings supply power to the two sets of CSR half-bridge arm circuits respectively. The voltage of the two windings is equal and the corresponding phases are the same. Each winding drives one set of CSR half-bridge arm circuits. The two sets of CSR half-bridge arm circuits work during their respective working times, and the working time corresponds to an angle range of 60°, forming an alternating working mode with complementary time, thus completing the high-frequency rectification function of the full-bridge CSR. The two sets of CSR half-bridge arms include a first CSR half-bridge circuit and a second CSR half-bridge circuit. The first CSR half-bridge circuit includes three bridge arms. The upper arm of each bridge consists of a diode and a switching transistor connected in series. The anode of the diode is connected to the AC input terminal, the cathode of the diode is connected to the collector of the switching transistor, and the emitter of the switching transistor is connected to the positive output of the rectifier bridge. The lower arm of each of the three bridge arms is a diode. The anode of the diode is connected to the negative output of the bridge arm, and the cathode is connected to the AC input terminal. The second CSR half-bridge circuit includes three bridge arms. The lower arm of each bridge consists of a diode and a switching transistor connected in series. The cathode of the diode is connected to the AC input terminal, the anode of the diode is connected to the collector of the switching transistor, and the emitter of the switching transistor is connected to the negative output of the rectifier bridge. The upper arm of each of the three bridge arms is a diode. The cathode of the diode is connected to the positive output of the bridge arm, and the anode is connected to the AC input terminal.

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