Energy Saving of Three-Phase CSR Rectifier Circuit and Wiring Method of Parallel Superposition

Abstract

The present invention discloses an energy-saving and parallel superposition wiring method for a three-phase CSR rectifier circuit in which two windings are output on the low-voltage side of a power distribution transformer, the two windings respectively supply power to two CSR half-bridge rectifier circuits, the voltages of the two windings are equal, and the phases of the corresponding phases are the same. Each of the windings has a set of CSR non-full-bridge circuits, and each of the two sets of CSR non-full-bridge circuits operates during its respective operating time, and the corresponding angular interval of the operating time is 60°, forming an interactive mode, where the times complement each other to complete the full-bridge CSR high-frequency rectification function. The present invention provides an energy-saving and parallel superposition wiring method for a three-phase CSR rectifier circuit with reduced switch tubes, reduced power consumption, high withstand voltage, large power factor, small harmonics, and increased power.

Description

Technical Field

[0001] The present invention relates to the technical field of CSR rectifier circuits, and particularly to energy saving of three-phase CSR rectifier circuits and wiring methods for parallel superposition.

Background Art

[0002] A CSR rectifier circuit is a high-frequency PWM (pulse width modulation) current source step-down rectifier power supply circuit. A high-power rectifier circuit also uses a three-phase input power supply. As shown in FIG. 1, it is a topology map of a three-phase 6-switch CSR rectifier circuit used in the prior art.

[0003] The conventional CSR rectifier circuit has the characteristics of high power factor of the PFC function and high output power control accuracy. Currently, the CSR rectifier circuit realizes high-frequency operation with high-power switches. When the circuit operating frequency is high, the generated harmonics are small.

[0004] The on-off control of the switch tube in the conventional CSR rectifier circuit is completed by a control circuit. The control circuit adjusts the on-pulse width, that is, PWM, according to the demand of the load magnitude. The determination of the pulse width is obtained by modulating a triangular wave carrier from a sine wave. Since the power supply is a sine wave, in order to improve the power factor, a sine wave is used as the modulation wave, and the magnitude of the current and the magnitude of the voltage are synchronously changed, which is also called an SPWM high-frequency rectifier power supply. S represents a sine wave, and hereinafter, it is represented by PWM.

[0005] Currently, high-power rectifier control is completed using a dedicated DSP digital signal controller, and the principle is the same as triangular wave modulation. Since the loss of the rectifier circuit is mainly the loss during the switching process and saturation conduction of the switch tube, reducing the number of operations of the switch tube is the main task of the present invention.

[0006] Also, in many cases, the CSR rectifier circuit needs to operate in a high-voltage and large-current situation. Currently, in the transistor manufacturing technology, the operating speed of a high-voltage and large-current switch tube is not very fast. Therefore, to achieve the goals of high power factor, small harmonics generated in the circuit, and large power, the operating frequency of the circuit needs to be greater than 20 kHz. Thus, it must be completed by parallel superimposing multiple sets of CSR rectifier circuits.

Summary of the Invention

Problems to be Solved by the Invention

[0007] In view of this, the present invention provides an energy-saving and parallel superimposing wiring method for a three-phase CSR rectifier circuit with reduced switch tubes, reduced power consumption, high breakdown voltage, large power factor, small harmonics, and increased power.

Means for Solving the Problems

[0008] To achieve the object of the present invention, the following technical solutions can be used.

[0009] An energy-saving and parallel superimposing wiring method for a three-phase CSR rectifier circuit, wherein two windings are output on the low-voltage side of the power distribution transformer, and the two windings respectively supply power to two sets of CSR half-bridge rectifier circuits. The voltages of the two windings are equal, and the phases of the corresponding phases are the same.

[0010] Each of the windings has a set of CSR non-full-bridge circuits. The two sets of CSR non-full-bridge circuits operate at their respective operating times, and the corresponding angular intervals of the operating times are 60°. An interactive mode is formed, and the times complement each other to complete the CSR high-frequency rectification function of the full bridge.

[0011] The two sets of CSR non-full-bridge circuits may be parallel superimposed as multiple sets of CSR non-full-bridge circuits.

[0012] Advantages of the present invention: In the present invention, the circuit loss is reduced by reducing the number of switching tubes operating in the CSR rectifier circuit. Specifically, two windings are output on the low-voltage side of the power distribution transformer, and the two windings have equal voltage and are not electrically connected, and each has one CSR non-full-bridge circuit. The two sets of circuits operate at their respective operating times, and the corresponding angles of the operating times are 60°, forming an alternating mode, and the operating times complement each other. When viewed from the input on the primary side of the transformer, the current sine wave is not distorted, and the perfect "full-bridge" CSR high-frequency rectification function is completed. Also, two windings are output on the low-voltage side of the power distribution transformer of the present invention, and each has one set of CSR half-bridge circuits. The upper and lower two sets of half-bridges each have one energy storage inductor. The operation of the circuit has symmetry and can fully realize parallel superposition, achieving the effect of increasing the output power.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0014] Hereinafter, the invention will be described in more detail with reference to the drawings and embodiments of the present invention.

[0015] In the present invention, a wiring method for energy saving and parallel superposition of a three-phase CSR rectifier circuit is proposed.

[0016] Referring to Fig. 1, the characteristics of the conventional three-phase CSR rectifier circuit are that commutation occurs between the upper and lower bridge arm switches of adjacent phases. Fig. 1 is a topology map of the CSR rectifier circuit. Here, V1, V2, and V3 are the upper bridge arm switch tubes of phases A, B, and C, D1, D2, and D3 are the upper bridge arm diodes of phases A, B, and C, V4, V5, and V6 are the lower bridge arm switch tubes of phases A, B, and C, D4, D5, and D6 are the lower bridge arm diodes of phases A, B, and C, L4 is an energy storage inductor, and D7 is a freewheel diode.

[0017] The power supply of the conventional three-phase CSR rectifier circuit is provided by one winding of a distribution transformer. At any moment during the operation of the CSR rectifier circuit, only one of the three switch tubes in the upper bridge arm and only one of the three switch tubes in the lower bridge arm are turned on so as to form a phase rectification closed circuit. For example, when the switch tube V1 in the upper bridge arm turns on the lower bridge arm, it means turning on one of the switch tubes V5 or V6 to form a current path. Each of the other switch tubes operates similarly.

[0018] Referring to Fig. 2, Fig. 2 is a three-phase sine wave waveform diagram of the three-phase CSR rectifier circuit. In Fig. 2, Ua, Ub, and Uc represent the voltage passing time (or angle) curves of phases A, B, and C. Arbitrarily select point D on the time line in Fig. 2. At this time, the corresponding voltage values of phases A, B, and C are points F, G, and E respectively.

[0019] According to the operating principle of the CSR circuit, the operating voltage at this point should be Uab (the line segment FG represents the magnitude of Uab) or Ubc (the line segment EG represents the magnitude of Ubc). Taking the operation of voltage Uab as an example, in FIG. 1, the corresponding switch tubes V1 and V5 are turned on, and the current i flows out from phase A as shown by the dashed line in FIG. 1, passes through V1, D1, L4, load RL, and V5, D5, and then flows back to phase B. In this process, in the CSR circuit, the main elements that generate losses are two switch tubes V1, D1, V5, D5 and two diodes. Similarly, every time during the turn-on process, losses of two switch tubes and two diodes occur, and it can be analyzed that the losses of the switch tubes are much larger than those of the diodes. Reducing the number of switch tubes is the main task of the present invention.

[0020] In the present invention, the circuit loss is reduced by reducing the number of switch tubes operating in the conventional CSR rectifier circuit.

[0021] Specifically, two windings are output on the low-voltage side of the power distribution transformer. The two windings have equal voltages, are not electrically connected, and each has one CSR non-full-bridge circuit. The two sets of circuits operate at their respective operating times, and the corresponding angles of the operating times are 60°. An alternating mode is formed, and the operating times complement each other. When viewed from the input on the primary side of the transformer, the current sine wave is not distorted, and a perfect "full-bridge" CSR high-frequency rectification function is completed.

[0022] Referring to FIG. 3, the power distribution transformer 1 has a high-voltage power grid connected to its primary side, and two windings are output on its secondary side, namely the first winding and the second winding. The two windings have equal voltages and the corresponding phases of each phase are the same. Each of the two windings has its own CSR half-bridge circuit.

[0023] As shown in Fig. 3, the combination of the first winding's first CSR half - bridge circuit 2, the power distribution transformer 1, and the first CSR half - bridge circuit 2 is called the upper half, and the combination of the second winding's second CSR half - bridge circuit 3, the power distribution transformer 1, and the second CSR half - bridge circuit 3 is called the lower half.

[0024] Different from the conventional CSR full - bridge circuit, the CSR half - bridge circuit described in the present invention, as shown in Fig. 1, the conventional CSR full - bridge circuit has three symmetric switch tubes and diodes in each of the upper and lower bridge arms.

[0025] As shown in Fig. 3, what is shown in the dashed - line box 2 in Fig. 3 is the upper - half first CSR half - bridge circuit 2 of the present invention.

[0026] In the first CSR half - bridge circuit 2, three switch tubes of the lower bridge arm of the conventional circuit are removed. As the specific configuration of the upper - half first CSR half - bridge circuit 2, the upper half - bridge is composed of switch tubes V11, V12, V13 and diodes D11, D12, D13, and the lower half - bridge is composed of diodes D14, D15, D16.

[0027] As shown in Fig. 3, in the lower - half second CSR half - bridge circuit 3, three switch tubes of the upper bridge arm of the conventional circuit are removed. As the specific configuration of the second CSR half - bridge circuit 3, the upper half - bridge is composed of diodes D21, D22, D23, and the lower half - bridge is composed of switch tubes V24, V25, V26 and diodes D24, D25, D26.

[0028] The corresponding angles of the operating times of the upper and lower halves are strictly defined. The operating interval of the upper half is 0° - 60°, 120° - 180°, 240° - 300°... and the operating interval of the lower half is 60° - 120°, 180° - 240°, 300° - 360°...

[0029] Regarding the specific operation process, when analyzing with reference to FIGS. 2 and 3, in FIG. 2, the voltage operation interval is 0° to 60°, and at this time, the CSR half-bridge circuit 2 in the upper half of the first winding of the distribution transformer 1 operates. In the CSR circuit 3 in the lower half of the second winding of the transformer, all the switch tubes are in the off state. During this period, the lower half does not operate, that is, V24, V25, V26 (including V224, V225, V226) are all off. Arbitrarily select point D in FIG. 2. As a CSR circuit characteristic, the operating voltage at this time is Uab or Ubc. Assuming that the operating voltage is Uab, in the operating process, V11 turns on, and the current flows from phase A through D11, V11, L14, load RL, and D15 back to phase B, which is the flowing direction of the current i in the upper half CSR half-bridge circuit 2 as shown in FIG. 3. The corresponding voltage values of the three phases A, B, and C at point D are points F, G, and E respectively. Thus, it can be seen that the phase B voltage in the 0° to 60° interval is the lowest, and the lower bridge arm has three diodes D14, D15, D16 of the three phases. Since the current can only flow back from phase B with the lowest potential, the current of phase A can only flow back from D15 of phase B and cannot flow back from phase C. Therefore, in the process of Uab operating, in the CSR circuit, the main loss-generating elements are one switch tube and two diodes, namely D11, V11, and D15. This process reduces the loss of one switch tube compared with the conventional CSR operation.

[0030] Similarly, assuming that the voltage Ubc near point D operates, at this time, the V13 tube turns on, and the current flows from phase C through D13, V13, L14, load RL, and D15 back to phase B. Since the potential of phase B is the lowest in the 0° to 60° interval, the current of phase C can only flow back from the diode D15 of phase B and cannot flow back from phase A.

[0031] Therefore, in the process of Ubc operation, in the CSR circuit, as the elements that generate losses, there is one switch tube and two diodes, namely D13, V13, and D15. In this process, the loss of one switch tube also decreases compared to the conventional CSR operation.

[0032] As shown in Fig. 2, the voltage operates in the range of 60° - 120°. At this time, the second winding of the distribution transformer 1 and the lower half of the second CSR half-bridge circuit 3 operate. All the switch tubes in the upper half of the CSR half-bridge circuit 2 of the first winding of the distribution transformer 1 are turned off, that is, V11, V12, V13 (including V121, V122, V123) are all turned off, and during this period, the upper half does not operate.

[0033] Arbitrarily select point H in Fig. 2. At this time, the corresponding points of the voltage values of the three phases A, B, and C are K, J, and I respectively. The three phases of the upper bridge arm have three diodes D21, D22, and D23. It can be seen that since the potential of phase A in the range of 60° - 120° is the highest, the current can only flow out from the diode D21 of phase A and cannot flow out from the diodes D22 and D23 of phases B and C. As a characteristic of the CSR circuit, the operating voltage at this time is only Uab or Uac. Taking the operation of Uab voltage as an example, turn on V25, and the current flows back from phase B through V25. The current-carrying elements are D21, load RL, L24, V25, and D25, and it returns to phase B. In this process, as the elements that generate losses in the CSR half-bridge circuit, there is one switch tube and two diodes, namely D21, V25, and D25. Compared with the operation of the conventional CSR rectifier circuit, the loss of one switch tube decreases. Similarly, analyzing the situation of the operating loss of voltage Uac is the same.

[0034] Similarly, since the potential of phase C is the lowest in the range of 120° to 180°, for CSR circuit identification, at this time, only the voltages Uac and Ubc can operate, and the currents of phases A and B can only flow back from phase C. Similarly, when analyzing the voltages Uac and Ubc, in the operating process, the elements that generate losses in the CSR half-bridge circuit are also one switch tube and two diodes.

[0035] The upper and lower half-bridge circuits are converted once every 60°, and the control method is executed according to the above principle, perfectly completing the CSR symmetric rectification operation. There are losses of two switch tubes and two diodes in the conventional CSR full-bridge rectifier circuit, and the loss of one switch tube is saved by the CSR half-bridge rectification of the present invention.

[0036] The loss of the switch tube is composed of two parts: switching process loss and saturation conduction voltage drop loss. Its saturation conduction voltage drop is about 3V. When there is a current of 50A in the circuit, at this time, the saturation conduction loss of the switch tube is 150W, and the switching process loss is more than three times the saturation conduction loss. The diode voltage drop is less than 1V. When the circuit has a current of 50A, the loss of the diode is less than 50W. Therefore, the operation of one switch tube is saved in the CSR half-bridge rectifier circuit of the present invention, which is equivalent to a reduction of more than 30% in circuit loss.

[0037] According to the current transistor manufacturing process, the operating frequency of high-voltage and high-power switch tubes cannot be increased too much. To improve the power factor, reduce harmonics, and improve the power output in the CSR rectifier circuit, multiple sets of CSR rectifier circuits need to operate in parallel and superimposed.

[0038] The bridge end output circuit of the conventional CSR full-bridge rectifier circuit can only have one energy storage inductor. As shown by L4 in Figure 1, it makes the output circuit asymmetric. When the voltage operates in the upper half cycle of the sine wave in Figure 2, they can be superimposed in parallel, but cannot be paralleled in the lower half cycle, resulting in the inability to superimpose multiple sets of CSR rectifier circuits in parallel.

[0039] In the present invention, two windings are output on the low-voltage side of the distribution transformer 1. The two windings have equal voltages, are not electrically connected, and each has a set of CSR half-bridge circuits, constituting the upper and lower halves. Since the upper and lower half-bridges each have one energy storage inductor, in this way, the operation balance of the upper and lower half cycles of the voltage sine wave is achieved, and the two halves are combined to complete the full-symmetric CSR rectification operation.

[0040] As shown in Figure 3, the two half-bridges in the upper half each have an inductor L14 and L124, and the two half-bridges in the lower half each have an inductor L24 and L224. The operation of the circuit has symmetry and can fully realize parallel superposition.

[0041] As shown in Figure 3, the first CSR half-bridge circuit 2 in the upper half includes a first parallel superposition circuit 4, and the first parallel superposition circuit 4 is the second set of CSR half-bridge circuits in the upper half. The specific configuration includes switch tubes V121, V122, V123 and diodes D121, D122, D123. The inductor L124 is the storage element of the half-bridge of the first parallel superposition circuit 4. In the first parallel superposition circuit 4, the current of each switch tube returns to the power supply side after flowing through the diodes D14, D15, D16 in the first CSR half-bridge circuit 2 after the load functions.

[0042] Referring to FIG. 3, the second CSR half-bridge circuit 3 includes a second parallel superimposing circuit 5, and the second parallel superimposing circuit 5 is the lower half of the second set of CSR half-bridge circuits. As a specific configuration, there are switch tubes V224, V225, V226 and diodes D224, D225, D226, and the inductor L224 is the energy storage element of the half-bridge of the second parallel superimposing circuit 5.

[0043] In the second parallel superimposing circuit 5, the current of each switch tube flows through the diodes D21, D22, D23 in the second CSR half-bridge circuit 3 and returns to the power supply side after the load functions. Here, D14, D15, D16 are the common diodes for the return current of each set in the upper half, and D21, D22, D23 are the common diodes for the output current of each set in the lower half.

[0044] JPEG2025519783000002.jpg51170

[0045] In the present invention, the circuit loss is reduced by reducing the number of switching tubes operating in the CSR rectifier circuit. As a specific method, two windings are output on the low-voltage side of the power distribution transformer. The two windings have equal voltages, are not electrically connected, and each has one CSR non-full-bridge circuit, forming two sets of upper and lower circuits. The CSR non-full-bridge circuit is one in which three switching tubes are removed from one set of upper bridge arms and another set of lower bridge arms, respectively. Each of the two sets of circuits operates during its respective operating time, and the corresponding angular interval of the operating time is 60°. The operations form an alternating mode, the times complement each other, and the current is not deformed into a sine wave, thus completing the full-bridge CSR high-frequency rectification function. The dashed box 2 and the dashed box 3 in FIG. 3 are two sets of upper and lower CSR half-bridge circuits, respectively. When each of the two half-bridge circuits operates, one switching tube is reduced compared to the conventional CSR full-bridge circuit, thus reducing the circuit loss. Also, two windings are output on the low-voltage side of the power distribution transformer, and each has one set of CSR half-bridge circuits. The two sets of upper and lower half-bridges each have one energy storage inductor. The operation of the circuit has symmetry and can fully realize parallel superposition, achieving the effect of increasing the output power.

Claims

1. A method for energy saving and parallel superposition wiring of a three-phase CSR rectifier circuit, wherein two windings are output on the low-voltage side of the power distribution transformer, and the two windings respectively supply power to two sets of CSR half-bridge rectifier circuits, and the two windings have equal voltage and the same phase of the corresponding phase. A method for energy saving and parallel superposition wiring of a three-phase CSR rectifier circuit, characterized in the above.

2. Each of the windings has a set of CSR non-full-bridge circuits, and each of the two sets of CSR non-full-bridge circuits operates during its respective operating time, and the corresponding angular interval of the operating time is 60°, forming an alternating operation mode, and the time complements each other to complete the full-bridge CSR high-frequency rectification function. The method for energy saving and parallel superposition wiring of a three-phase CSR rectifier circuit according to Claim 1, characterized in the above.

3. The two sets of CSR non-full-bridge circuits can be superimposed in parallel as a plurality of sets of CSR non-full-bridge circuits. The method for energy saving and parallel superposition wiring of a three-phase CSR rectifier circuit according to Claim 2, characterized in the above.

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