Voltage-type PWM rectifier module with DC-side current limiting operation and short-circuit protection

Abstract

This invention relates to a voltage-type PWM rectifier module with DC-side current-limiting operation and short-circuit protection, comprising a voltage-type PWM rectifier bridge, a current-limiting unit, a freewheeling unit, and a sampling and control unit connected in sequence. The AC-side PWM controller in the sampling and control unit outputs a control signal to the voltage-type PWM rectifier bridge to control the switching devices in the voltage-type PWM rectifier bridge to turn on or off. The DC-side current-limiting and protection controller in the sampling and control unit outputs a control signal to the current-limiting unit to control the switching devices in the current-limiting unit to turn on or off. By connecting the current-limiting unit in series and the freewheeling unit in parallel on the DC side of the voltage-type PWM rectifier bridge, supplemented by current-limiting and protection strategies, effective protection of the voltage-type PWM rectifier bridge devices is achieved, and current-limiting operation is also provided. Only a few additional components are added, effectively overcoming the shortcomings of the original technology, improving safety, and expanding the application range.

Description

Technical Field

[0001] This invention relates to the field of power electronics design, and in particular to a voltage-type PWM rectifier module with DC-side current-limiting operation and short-circuit protection. Background Technology

[0002] PWM rectifiers are widely used in controllable power supplies, frequency converters, permanent magnet generators and other fields. Among them, voltage-type PWM rectifiers have become the mainstream in medium and high power applications due to their simple structure and bidirectional energy transfer capability.

[0003] However, due to its inherent characteristics, when a short circuit occurs on the DC side of a voltage-source PWM rectifier, if the drive pulse of the switching device is blocked, its anti-parallel diode will still bear the short-circuit current. Therefore, effective protection of the device cannot be achieved by blocking the PWM pulse.

[0004] Existing technologies employ a solution that increases the current-carrying capacity of anti-parallel diodes, relying on the tripping action of the upstream circuit breaker to achieve protection after the device withstands a short-circuit current for a certain period. Since the short-circuit current can typically be 4 to 10 times greater than the rated current during normal operation, this approach results in a large device size and low device utilization. Summary of the Invention

[0005] To address the aforementioned issues, a voltage-type PWM rectifier module with DC-side current-limiting operation and short-circuit protection is proposed.

[0006] The technical solution of the present invention is: a voltage-type PWM rectifier module with DC-side current limiting operation and short-circuit protection, comprising a voltage-type PWM rectifier bridge, a current limiting unit, a freewheeling unit, and a sampling and control unit connected in sequence;

[0007] The voltage-type PWM rectifier bridge is composed of several half-bridge branches connected in parallel and then connected in parallel with the bus support capacitor. Each half-bridge branch consists of two switching devices connected in series, and the series connection point of each half-bridge branch is connected to the corresponding AC input terminal. The DC current output from both ends of the bus support capacitor enters the current limiting unit.

[0008] The current limiting unit includes a switching device and a reverse protection diode connected in parallel;

[0009] The freewheeling unit includes a diode;

[0010] The positive DC output of the voltage-type PWM rectifier bridge is connected to the output of the switching device of the series current limiting unit, which is the output of the voltage-type PWM rectifier module (DC+). The negative DC output of the voltage-type PWM rectifier bridge is connected to the output of the voltage-type PWM rectifier module (DC-).

[0011] The diode of the freewheeling unit is connected in parallel across the positive and negative terminals of the output of the voltage - type PWM rectifier module. The anode of the diode of the freewheeling unit is connected to the output terminal DC -, and the cathode of the diode of the freewheeling unit is connected to the output terminal DC +.

[0012] The sampling and control unit includes an AC - side PWM controller and a DC - side current - limiting and protection controller. The sampling and control unit respectively collects the current and voltage signals at the AC input terminals of the voltage - type PWM rectifier bridge and sends the collected signals to the AC - side PWM controller.

[0013] The sampling and control unit collects the current signal output from the output terminal DC + of the voltage - type PWM rectifier module and the voltage signal between the output terminal DC + and the output terminal DC -, and sends the collected signals to the AC - side PWM controller and the DC - side current - limiting and protection controller.

[0014] The AC - side PWM controller outputs control signals to the voltage - type PWM rectifier bridge to control the on - off of the switching devices in the voltage - type PWM rectifier bridge.

[0015] The DC - side current - limiting and protection controller outputs control signals to the current - limiting unit to control the on - off of the switching devices in the current - limiting unit.

[0016] Preferably, if the voltage - type PWM rectifier bridge is composed of 2 parallel half - bridge branches, it is a single - phase full - bridge PWM rectification; if the voltage - type PWM rectifier bridge is composed of 3 half - bridge branches, it is a three - phase half - bridge PWM rectification.

[0017] For the control method of the voltage - type PWM rectifier module with DC - side current - limiting operation and short - circuit protection, the AC - side PWM controller adopts a rectification control method. Through DC voltage closed - loop, AC current closed - loop and decoupling control, the control signals of the voltage - type PWM rectifier bridge are finally generated.

[0018] Furthermore, the DC - side current - limiting and protection controller judges the DC - side current signal collected in real - time: when the DC - side current value is less than the current - limiting point current value I1, it controls the switching devices of the current - limiting unit to conduct continuously; when the DC - side current value is greater than or equal to the current - limiting point current value I1 and less than the short - circuit protection point current value I2, it controls the switching devices of the current - limiting unit to conduct intermittently in a PWM mode with a duty cycle D; when the DC - side current value is greater than or equal to the short - circuit protection point current value I2, it controls the switching devices of the current - limiting unit to turn off.

[0019] Furthermore, the current - limiting point current value I1 < the short - circuit protection point current value I2; 0 < D < 1; the current - limiting point current value I1 is set according to the overload operation requirements of the voltage - type PWM rectifier module; the protection point current value I2 is set according to the current - carrying capacity of the voltage - type PWM rectifier module to prevent the protection device from being damaged due to over - current.

[0020] Furthermore, the PWM mode of the duty cycle D is obtained by a hysteresis comparator:

[0021] Let the hysteresis width be H. When the PWM is high and the current limiting unit switch is turned on, the DC-side load receives voltage and the current rises until the DC-side current rises to I1+0.5H. Then, the PWM is set to low and the current limiting unit switch is turned off. Then, the DC-side load loses voltage and the current drops until the DC-side current drops to I1-0.5H. Then, the PWM is set to high again and the current limiting power supply switch is turned on. This cycle repeats, thus limiting the DC-side current to the hysteresis range of I1±0.5H.

[0022] Furthermore, the PWM mode of the duty cycle D is obtained by the PI controller: the input of the PI controller is the difference between the current limit point current value I1 and the DC side current value, and the output is the PWM duty cycle D. The smaller the difference, the smaller the duty cycle.

[0023] The beneficial effects of this invention are as follows: The DC-side current-limiting operation and short-circuit protection voltage-type PWM rectifier module of this invention, by connecting a current-limiting unit in series and a freewheeling unit in parallel on the DC side of a conventional voltage-type PWM converter, and supplementing it with appropriate current-limiting and protection strategies, effectively protects the devices of the voltage-type PWM converter and provides current-limiting operation functionality. It adds only a few components, effectively overcoming the shortcomings of the original technology, improving safety, and expanding the application range. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the voltage-type PWM rectifier module structure for DC-side current limiting operation and short-circuit protection according to the present invention;

[0025] Figure 2 This is a control strategy diagram of the DC-side current limiting and protection controller of the present invention;

[0026] Figure 3 Generate a PWM diagram for the hysteresis comparator of this invention;

[0027] Figure 4 Generate a PWM diagram for the PI controller of this invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0029] like Figure 1The diagram shows the structure of a voltage-type PWM rectifier module with DC-side current limiting operation and short-circuit protection; the module includes a voltage-type PWM rectifier bridge, a current limiting unit, a freewheeling unit, and a sampling and control unit;

[0030] The voltage-type PWM rectifier bridge is composed of several groups of half-bridge branches (P(1) to P(N)) connected in parallel and then connected in parallel with the bus support capacitor. Each half-bridge branch consists of two switching devices connected in series, and each switching device is connected in parallel with a reverse protection diode. In each half-bridge branch, the emitter of the upper arm switching device is connected to the collector of the lower arm switching device, and the connection point is connected to the corresponding AC input terminal (AC(1) to AC(N)). The collectors of the upper arm switching devices of each group of half-bridge branches are connected to each other and connected to one pole of the bus support capacitor as the positive pole of DC output. The emitters of the lower arm switching devices of each half-bridge branch are connected to each other and connected to the other pole of the bus support capacitor as the negative pole of DC output.

[0031] When the voltage-type PWM rectifier bridge is composed of two half-bridge branches connected in parallel, it is a single-phase full-bridge PWM rectifier; when the voltage-type PWM rectifier bridge is composed of three half-bridge branches, it is a three-phase half-bridge PWM rectifier.

[0032] The current limiting unit includes a switching device and a reverse protection diode connected in parallel.

[0033] The freewheeling unit contains a diode.

[0034] The positive DC output of the voltage-type PWM rectifier bridge is connected to the output terminal DC+ of the voltage-type PWM rectifier module via the switching device of the series current limiting unit, and the negative DC output of the voltage-type PWM rectifier bridge is connected to the output terminal DC- of the voltage-type PWM rectifier module. The diode of the freewheeling unit is connected in parallel to the positive and negative output terminals of the voltage-type PWM rectifier module, with the anode of the diode connected to the output terminal DC- and the cathode connected to the output terminal DC+.

[0035] The sampling and control unit includes AC side current and voltage sampling, DC side current and voltage sampling, AC side PWM controller and DC side current limiting and protection controller.

[0036] The AC side current and voltage sampling acquires the current and voltage signals of the AC input terminals (AC(1)~AC(N)) of the voltage-type PWM rectifier bridge, and sends the acquired signals to the AC side PWM controller; the DC side current and voltage sampling acquires the current signal output from the DC+ output terminal of the voltage-type PWM rectifier module with DC side current limiting operation and short circuit protection, as well as the voltage signal between the output terminal DC+ and the output terminal DC-, and sends the acquired signals to the AC side PWM controller and the DC side current limiting and protection controller.

[0037] The AC-side PWM controller executes a rectification control method. Through DC voltage closed-loop, AC current closed-loop, and decoupling control, it finally generates a control signal for the voltage-source PWM rectifier bridge to control the on or off of the switching devices in the voltage-source PWM rectifier bridge.

[0038] The present invention also provides a control strategy for the DC-side current limiting and protection controller, such as Figure 2 shown. The DC-side current limiting and protection controller judges the DC-side current signal collected in real time: when the DC-side current value is less than the current limiting point current value I1, it controls the switching device of the current limiting unit to conduct continuously; when the DC-side current value is greater than or equal to the current limiting point current value I1 and less than the short-circuit protection point current value I2, it controls the switching device of the current limiting unit to conduct intermittently in a PWM mode with a duty cycle D; when the DC-side current value is greater than or equal to the short-circuit protection point current value I2, it controls the switching device of the current limiting unit to turn off.

[0039] Among them, the current limiting point current value I1 < the short-circuit protection point current value I2; 0 < D < 1; the current limiting point current value I1: According to the overload operation requirements of the voltage-source PWM rectification module, if the overload coefficient is k1 (generally: 1 < k1 ≤ 1.5), then I1 is k1 times the rated DC output current I0, that is, I1 = k1 * I0; the protection point current value I2: According to the current-carrying capacity of the voltage-source PWM rectification module, to protect the device from being damaged due to overcurrent, the protection point current value is k2 (generally: 1.6 ≤ k2 < 2) times the rated current, that is, I2 = k2 * I0.

[0040] The PWM with the duty cycle D can be obtained by a hysteresis comparator ( Figure 3 ); it can also be obtained by a PI controller ( Figure 4 ).

[0041] Such as Figure 3 shown. When using a hysteresis comparator, let the hysteresis width be H. When PWM is at a high level (the switching device of the current limiting unit is conducting), the DC-side load obtains voltage and the current rises. Until the DC-side current rises to I1 + 0.5H, it controls PWM to be at a low level (the switching device of the current limiting unit is turned off); then the DC-side load loses voltage and the current drops. Until the DC-side current drops to I1 - 0.5H, it controls PMW to be at a high level again (the switching device of the current limiting power supply is conducting). In this way, the DC-side current can be limited within the hysteresis range of I1 ± 0.5H.

[0042] Such as Figure 4 shown. When using a PI controller, the input of the PI controller is the difference between the current limiting point current value I1 and the DC-side current value, and the output is the PWM duty cycle D. The smaller the difference, the smaller the duty cycle.

[0043] When using a PI controller, the input to the PI controller is the difference between the current limiting point current value I1 (given) and the DC side current value (feedback). The output range of the PI controller is controlled as follows: when the difference is positive, the output PWM duty cycle D is 1, which is equivalent to not triggering the current limiting effect; when the difference is negative, the output PWM duty cycle D takes a value between 0 and 1, thereby achieving current limiting. Under the adjustment of the PI controller, the DC side current value will be limited to around I1.

[0044] Figure 4 In the PI controller, the carrier wave is a sawtooth wave with 0 at the trough and 1 at the peak. When the duty cycle is greater than the carrier value, the PWM is set to high level (the current limiting unit switch is turned on); when the duty cycle is less than the carrier value, the PWM is set to low level (the current limiting unit switch is turned off).

[0045] If the DC current value continues to rise rapidly after the current limiting unit activates and exceeds the protection current point I2, the protection function will be triggered, blocking the PWM pulse of the current limiting unit's switching device, turning off the current limiting unit's switching device, and cutting off the power to the DC output side, thereby protecting the voltage-type PWM rectifier module and the system.

[0046] The embodiments described above merely illustrate specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A control method for a voltage - type PWM rectifier module with DC - side current limiting operation and short - circuit protection. The voltage - type PWM rectifier module includes a voltage - type PWM rectifier bridge, a current - limiting unit, a free - wheeling unit, and a sampling and control unit connected in sequence; The voltage - type PWM rectifier bridge is formed by paralleling several half - bridge branches and then paralleling with a bus - supporting capacitor. Each half - bridge branch is composed of two switching devices connected in series, and the series connection point of each half - bridge branch is connected to the corresponding AC input terminal; the direct current output from both ends of the bus - supporting capacitor enters the current - limiting unit; The current - limiting unit includes a switching device and its paralleled reverse - protection diode; The free - wheeling unit includes a diode; The positive DC output of the voltage - type PWM rectifier bridge is connected in series with the switching device of the current - limiting unit, and the output is the output terminal DC+ of the voltage - type PWM rectifier module. The negative DC output of the voltage - type PWM rectifier bridge is the output terminal DC - of the voltage - type PWM rectifier module; The diode of the free - wheeling unit is paralleled at both positive and negative output ends of the voltage - type PWM rectifier module. The anode of the diode of the free - wheeling unit is connected to the output terminal DC -, and the cathode of the diode of the free - wheeling unit is connected to the output terminal DC+; The sampling and control unit includes an AC - side PWM controller and a DC - side current - limiting and protection controller; the sampling and control unit respectively collects the current and voltage signals at the AC input terminals of the voltage - type PWM rectifier bridge and sends the collected signals to the AC - side PWM controller; The sampling and control unit collects the current signal output from the output terminal DC+ of the voltage - type PWM rectifier module and the voltage signal between the output terminal DC+ and the output terminal DC -, and sends the collected signals to the AC - side PWM controller and the DC - side current - limiting and protection controller; The AC - side PWM controller outputs a control signal to the voltage - type PWM rectifier bridge to control the turning - on or turning - off of the switching devices in the voltage - type PWM rectifier bridge; The DC - side current - limiting and protection controller outputs a control signal to the current - limiting unit to control the turning - on or turning - off of the switching device in the current - limiting unit; If the voltage - type PWM rectifier bridge is composed of 2 paralleled half - bridge branches, it is a single - phase full - bridge PWM rectification; or If the voltage - type PWM rectifier bridge is composed of 3 half - bridge branches, it is a three - phase half - bridge PWM rectification; The AC-side PWM controller employs a rectification control method, generating a voltage-type PWM rectifier bridge control signal through DC voltage closed-loop, AC current closed-loop, and decoupling control. Its key feature is that... The DC - side current - limiting and protection controller judges the real - time collected DC - side current signal: when the DC - side current value is less than the current - limiting point current value I1, it controls the switching device of the current - limiting unit to conduct continuously; when the DC - side current value is greater than or equal to the current - limiting point current value I1 and less than the short - circuit protection point current value I2, it controls the switching device of the current - limiting unit to conduct intermittently in a PWM mode with a duty cycle D; when the DC - side current value is greater than or equal to the short - circuit protection point current value I2, it controls the switching device of the current - limiting unit to turn off; The current - limiting point current value I1 < the short - circuit protection point current value I2; 0 < D < 1; the current - limiting point current value I1 is set according to the overload operation requirements of the voltage - type PWM rectifier module; the protection point current value I2 is set according to the current - passing capacity of the voltage - type PWM rectifier module to ensure that the protection device is not damaged due to over - current; The PWM mode of the duty cycle D is obtained by a hysteresis comparator: Let the hysteresis width be H. When the PWM is high, the current limiting unit switch is turned on, the DC-side load receives voltage, and the current rises until the DC-side current rises to I1+0.5H. Then, the PWM is controlled to be low, and the current limiting unit switch is turned off. Then the DC-side load loses voltage, and the current drops until the DC-side current drops to I1-0.5H. Then, the PWM is controlled to be high again, and the current limiting power supply switch is turned on. This cycle repeats, thus limiting the DC-side current within the hysteresis range of I1±0.5H. The PWM mode of the duty cycle D is obtained by the PI controller: the input of the PI controller is the difference between the current limit point current value I1 and the DC side current value, and the output is the PWM duty cycle D. When the difference is negative, the smaller the difference, the smaller the duty cycle.

Images