High-power IGCT converter clamping circuit optimization design method

Abstract

The invention provides an optimization design method for a clamping circuit of a high-power IGCT converter. The optimization design method comprises the following steps: step 1, analyzing an on-off transient process of the IGCT converter; step 2, solving expressions of all parts of the clamping circuit through quantitative analysis of the IGCT on-off transient process in the step 1, and analyzing the transfer direction of energy stored by the anode reactor to obtain expressions of energy in all directions; and according to an energy expression fed back to the direct current bus capacitor by the anode reactor in an analysis result, adjusting and optimizing a clamping capacitor parameter within an allowable range of maximum withstand voltage of the device, so that the energy fed back to the direct current bus by the anode reactor is maximum. By analyzing the transient process of the clamping circuit when the device is switched on and off, the parameter design of the clamping circuit is optimized, so that the efficiency improvement requirement of the anode reactor is met under the condition that the anode reactor has the corresponding current rise rate limiting capability. The cost of the clamping circuit can be reduced, and the operation efficiency of the clamping circuit is improved at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of converter design, and in particular to a high-power IGCT converter clamping circuit optimization design method. Background Art

[0002] High-power converters based on IGCT require clamping circuits to limit the current change rate when the IGCT is turned on and the diode is turned off. The parameter design of the clamping absorption circuit needs to comprehensively consider the influence of factors such as the withstand voltage of the IGCT device, the current change rate tolerance of the power device, the dynamic recovery time of the clamping circuit, and the loss of the clamping circuit. The parameters of the clamping absorption circuit will directly affect the device SOA and the minimum pulse width, and are a very important part in the design of the converter power module. Therefore, it is necessary to study the parameter design method of the converter absorption clamping circuit.

[0003] At present, the general method of clamping circuit design is to use parameters such as IGCT terminal voltage and circuit transition time as constraints to guide the parameter design of the clamping circuit. The main purpose is to meet the limitations of actual device parameters while considering the minimum turn-off time limit of IGCT. Loss optimization is not involved.

[0004] In a switching cycle, as the power devices are turned on and off, the energy on the anode reactor is first charged and then lost. Currently, there is no optimized design method for the clamping circuit to address this part of the loss. Summary of the invention

[0005] The present invention provides a high-power IGCT converter clamping circuit optimization design method, for the IGCT converter clamping circuit anode reactor L i The energy transfer is analyzed and calculated, and the circuit is optimized to improve the efficiency of the clamping circuit.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: A high-power IGCT converter clamping circuit optimization design method, the optimization design method comprising: Step 1: Analyze the transient process of IGCT converter switching off; Step 2: By quantitatively analyzing the IGCT switching transient process in step 1, the expressions of each part of the clamping circuit are solved, and the transfer destination of the energy stored in the anode reactor is analyzed to obtain the expressions of the energy in each destination; according to the energy expression of the anode reactor fed back to the DC bus capacitor in the analysis results, within the allowable range of the maximum withstand voltage of the device, the clamping capacitor parameters are adjusted and optimized to maximize the energy fed back to the DC bus by the anode reactor, so as to achieve the purpose of improving the efficiency of the clamping circuit.

[0007] The clamping circuit topology of the above IGCT converter is IGCT: Including DC bus capacitor C DC , DC bus capacitor C DC With anode reactor L i , IGCT converter, load inductor L Load To form a loop, clamping diode D CL and clamping capacitors C CL Then connect in series to the IGCT converter and load inductor in parallel L Load Both ends, clamp resistor R CL Connect the DC bus capacitors at both ends C DC With anode reactor L i , clamping diode D CL and clamping capacitors C CL The middle connection point of the load inductance L Load A fast recovery diode FWD is connected in parallel at both ends of the IGCT converter. 1 .

[0008] In the clamping circuit of the above IGCT converter, u Li (t) and i Li (t) represents the anode reactor L i The instantaneous voltage and instantaneous current at both ends, U CCL (t) and i CCL (t) represents the clamping capacitance C CL The instantaneous voltage and instantaneous current at both ends, U CDC and U T Represent the voltage across the DC capacitor and IGCT respectively, V D represents the steady-state voltage across the DC capacitor, i R (t) and I L Respectively represent the clamping resistance R CL and load inductance L Loadof current.

[0009] The analysis process of the IGCT converter switching transient process in step 1 above is as follows: In the transient process of breaking: IGCT is turned on, fast recovery diode FWD is turned off, and reverse recovery current is generated I rr ; At this time, the anode reactor L i The peak current passing through the IGCT is the load current I L The reverse recovery current of the fast recovery diode FWD I rr The sum of the anode reactor over time L i Current on i Li (t) Gradually reduce to load current I L ; In the shutdown transient state: ICGT is turned off, the fast recovery diode FWD is turned on, and the load inductance L Load Load current on I L The load inductance L Load The closed loop composed of the fast recovery diode FWD consumes the anode inductor. L i Current on i Li (t) From load current I L Finally, it drops to 0. Since the IGCT is turned off during this process, the anode reactor L i All the electrical energy on the capacitor is transferred through the clamping circuit.

[0010] In the above step 2, the quantitative analysis process of the IGCT switching transient process in step 1 specifically includes: Since the IGCT's on-off transient time is much smaller than the circuit time constant, it is assumed in the analysis that the IGCT and the anti-parallel diode are turned on and off instantly; when the IGCT is turned on, the fast recovery diode FWD is turned off, generating a reverse recovery current. I rr ; At this time, the anode reactor L i The peak current passing through the IGCT is the load current I L The reverse recovery current of the fast recovery diode FWD I rr Therefore, the maximum energy stored in the anode reactor during a switching cycle is: ; (1) As time goes by, the anode reactor L i Current i Li (t) Gradually reduce to load current I L , so during the switching process, the energy dissipated by the anode reactor is: ; (2) In the turn-off transient state: ICGT is turned off, and the fast recovery diode FWD is turned on, and the load inductance L Load Load current on I L The anode reactor is consumed in the closed loop composed of the load reactance and the fast recovery diode FWD. L i Current on i Li (t) From load current I L Finally it drops to 0. Therefore, when the IGCT is turned off, the anode reactor L i The dissipated energy is: ; (3) Since the IGCT is in the off state during this process, the anode reactor L i All the electric energy on the anode reactor is transferred through the clamping circuit; From formulas (2) and (3), it can be seen that in one switching cycle, the anode reactor L i The total dissipated energy is given by equation (1), the anode reactor L i The energy dissipated in one cycle is proportional to the square of the sum of the load current and the reverse recovery current, which limits the efficiency improvement of the circuit. Therefore, it is necessary to analyze the anode reactor. L i The transfer direction of energy on the DC bus allows more energy to be fed back to the DC bus capacitor. C DC superior.

[0011] In the above step 2, the analytical process of the expressions of each part of the clamp circuit is: The IGCT turn-off transient process is analyzed and deduced by formulas (1)-(3). The clamping capacitor U CCL The expression of (t) is: ; (4) Where D is the damping coefficient,ω 0 is the natural frequency: ; (5) During the IGCT turn-off transient process, the IGCT terminal voltage depends on the voltage across the clamping capacitor. To facilitate analysis and calculation, it is necessary to simplify the voltage expression across the clamping capacitor. Substituting the damping coefficient and the natural frequency into equation (4), the voltage expression is a sinusoidal amplitude attenuation waveform, which can be simplified using an approximate triangle average value: ; (6) Theoretical analysis and derivation of the IGCT turn-off transient process, DC bus capacitor C DC Voltage across the terminals U CDC The terminal voltage at (t) is: ;(7).

[0012] In the above step 2, there are formulas (4)-(7) and the anode reactor L i The reasoning process for where the stored energy is transferred is: When the shutdown transient is complete, the DC bus capacitor C DC The stored energy is: ; (8) According to equation (8), during the shutdown process, the anode reactor L i Transfer to DC bus capacitor C DC The energy on is: ;(9).

[0013] In the above step 2, the transient process of IGCT opening is theoretically analyzed and derived, and the DC bus capacitance can be obtained by solving the second-order circuit. C DC Peak voltage across the terminals U CDC (t) max The terminal voltage is as follows: ; (10) According to formula (10), during the opening process, the anode reactor L i Transfer to DC bus capacitor C DC The energy on is: ;(11).

[0014] In the above step 2, according to the anode reactor in formula (11)L i Feedback to DC bus capacitor C DC The energy expression on the anode reactor is constant by adjusting the clamping capacitor. C CL Parameters, can increase the anode reactor L i Feedback to DC bus capacitor C DC The energy on the device; within the maximum withstand voltage range of the device, the clamping capacitance can be reduced C CL Capacitance, making the anode reactor L i The energy fed back to the DC bus is maximized, thereby improving the efficiency of the clamping circuit.

[0015] The present invention provides a high-power IGCT converter clamping circuit optimization design method. Based on the general anode reactor design method, the method analyzes the transient process of the clamping circuit when the device is disconnected, clarifies the energy transfer destination of the anode reactor, analyzes the energy fed back to the DC bus capacitor by the anode reactor, and optimizes the parameter design of the clamping circuit, thereby achieving the efficiency improvement demand of the anode reactor when the anode reactor has the corresponding current rise rate limiting capability. Compared with the existing scheme, by optimizing the energy fed back to the DC bus capacitor by the anode reactor, not only the cost of the clamping circuit can be reduced, but also the operating efficiency of the clamping circuit can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 A topological schematic diagram of an IGCT-based converter with a clamping circuit in the present invention; Figure 2 It is a schematic diagram of an enlarged process of the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following content will systematically and completely describe the specific technical solutions of the present invention in combination with the drawings provided according to the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0018] Embodiment 1: A high-power IGCT converter clamping circuit optimization design method, the optimization design method comprising: Step 1: Analyze the transient process of IGCT converter switching off; Step 2: By quantitatively analyzing the IGCT switching transient process in step 1, the expressions of each part of the clamping circuit are solved, and the transfer destination of the energy stored in the anode reactor is analyzed to obtain the expressions of the energy in each destination; according to the energy expression of the anode reactor fed back to the DC bus capacitor in the analysis results, within the allowable range of the maximum withstand voltage of the device, the clamping capacitor parameters are adjusted and optimized to maximize the energy fed back to the DC bus by the anode reactor, so as to achieve the purpose of improving the efficiency of the clamping circuit.

[0019] The clamping circuit topology of the above IGCT converter is: Including DC bus capacitor C DC , DC bus capacitor C DC With anode reactor L i , IGCT converter, load inductor L Load To form a loop, clamping diode D CL and clamping capacitors C CL Then connect in series to the IGCT converter and load inductor in parallel L Load Both ends, clamp resistor R CL Connect the DC bus capacitors at both ends C DC With anode reactor L i , clamping diode D CL and clamping capacitors C CL The middle connection point of the load inductance L Load A fast recovery diode FWD is connected in parallel at both ends, and an anti-reverse diode D is connected in parallel at both ends of the IGCT converter. 1 .

[0020] In the clamping circuit of the above IGCT converter, u Li (t) and i Li (t) represents the anode reactor L i The instantaneous voltage and instantaneous current at both ends, U CCL (t) and i CCL (t) represents the clamping capacitance C CL The instantaneous voltage and instantaneous current at both ends, UCDC and U T Represent the voltage across the DC capacitor and IGCT respectively, V D represents the steady-state voltage across the DC capacitor, i R (t) and I L Respectively represent the clamping resistance R CL and load inductance L Load of current.

[0021] The analysis process of the IGCT converter switching transient process in step 1 above is as follows: In the transient process of breaking: IGCT is turned on, fast recovery diode FWD is turned off, and reverse recovery current is generated I rr ; At this time, the anode reactor L i The peak current passing through the IGCT is the load current I L The reverse recovery current of the fast recovery diode FWD I rr The sum of the anode reactor over time L i Current on i Li (t) Gradually reduce to load current I L ; In the shutdown transient state: ICGT is turned off, the fast recovery diode FWD is turned on, and the load inductance L Load Load current on I L In load inductance L Load The closed loop formed by the fast recovery diode FWD is consumed in cycles, as shown in loop ①. L i Current on i Li (t) From load current I L Finally, it drops to 0. Since the IGCT is turned off during this process, the anode reactor L i All the electric energy on the DC bus is transferred through the clamping circuit, that is, the clamping capacitor is charged through loop ②, the electric energy is consumed on the clamping resistor through loop ③, and the electric energy is fed back to the DC bus through loop ⑤. The electric energy stored in the anode reactor during the switching transient process is transferred through loops ②, ③, and ⑤.

[0022] The anode reactor current at the initial turn-on is the sum of the load current and the diode reverse recovery current until it becomes the load current in the turn-on steady state; the anode reactor current at the initial turn-off is the load current, which is zero in the steady state. The current change reflects the change in the energy stored in the anode reactor. The dissipated energy goes to the heat of the clamping resistor and is fed back to the DC bus capacitor.

[0023] In the above step 2, the quantitative analysis process of the IGCT switching transient process in step 1 specifically includes: Since the IGCT's on-off transient time is much smaller than the circuit time constant, it is assumed in the analysis that the IGCT and the anti-parallel diode are turned on and off instantly; when the IGCT is turned on, the fast recovery diode FWD is turned off, generating a reverse recovery current. I rr ; At this time, the anode reactor L i The peak current passing through the IGCT is the load current I L The reverse recovery current of the fast recovery diode FWD I rr Therefore, the maximum energy stored in the anode reactor during a switching cycle is: ; (1) As time goes by, the anode reactor L i Current i Li (t) Gradually reduce to load current I L , so during the switching process, the energy dissipated by the anode reactor is: ; (2) In the turn-off transient state: ICGT is turned off, and the fast recovery diode FWD is turned on, and the load inductance L Load Load current on I L The anode reactor is consumed in the closed loop composed of the load reactance and the fast recovery diode FWD. L i Current on i Li (t) From load current I L Finally it drops to 0. Therefore, when the IGCT is turned off, the anode reactor L i The dissipated energy is: ; (3) Since the IGCT is in the off state during this process, the anode reactor Li All the electric energy on the anode reactor is transferred through the clamping circuit; from formulas (2) and (3), it can be seen that in one switching cycle, the anode reactor L i The total dissipated energy is given by equation (1), the anode reactor L i The energy dissipated in one cycle is proportional to the square of the sum of the load current and the reverse recovery current, which limits the efficiency improvement of the circuit. Therefore, it is necessary to analyze the anode reactor. L i The transfer of energy on the DC bus allows more energy to be fed back to the DC bus capacitor. C DC superior.

[0024] In the above step 2, the analytical process of the expressions of each part of the clamp circuit is: The IGCT turn-off transient process is analyzed and deduced by formulas (1)-(3). The clamping capacitor U CCL The expression of (t) is: ; (4) Where D is the damping coefficient, and D=0.8 is taken according to the empirical value method. ω 0 is the natural frequency: ; (5) During the IGCT turn-off transient process, the IGCT terminal voltage depends on the voltage across the clamping capacitor. To facilitate analysis and calculation, it is necessary to simplify the voltage expression across the clamping capacitor. Substituting the damping coefficient and the natural frequency into equation (4), the voltage expression is a sinusoidal amplitude attenuation waveform, which can be simplified using an approximate triangle average value: ; (6) Theoretical analysis and derivation of the IGCT turn-off transient process, DC bus capacitor C DC Voltage across the terminals U CDC The terminal voltage at (t) is: ;(7).

[0025] In the above step 2, there are formulas (4)-(7) and the anode reactor L i The reasoning process for where the stored energy is transferred is: When the shutdown transient is complete, the DC bus capacitor C DC The stored energy is: ; (8) According to equation (8), during the shutdown process, the anode reactorL i Transfer to DC bus capacitor C DC The energy on is: ;(9).

[0026] In the above step 2, the transient process of IGCT opening is theoretically analyzed and derived, and the DC bus capacitance can be obtained by solving the second-order circuit. C DC Peak voltage across the terminals U CDC (t) max The terminal voltage is as follows: ; (10) According to formula (10), during the opening process, the anode reactor L i Transfer to DC bus capacitor C DC The energy on is: ;(11).

[0027] In the above step 2, according to the anode reactor in formula (11) L i Feedback to DC bus capacitor C DC The energy expression on the anode reactor is constant by adjusting the clamping capacitor. C CL Parameters, can increase the anode reactor L i Feedback to DC bus capacitor C DC The energy on the device; within the maximum withstand voltage range of the device, the clamping capacitance can be reduced C CL Capacitance, making the anode reactor L i The energy fed back to the DC bus is maximized, thereby improving the efficiency of the clamping circuit.

Claims

1. A high-power IGCT converter clamping circuit optimization design method, characterized in that: Optimization design methods include: Step 1: Analyze the transient process of IGCT converter switching off; Step 2: By quantitatively analyzing the IGCT switching transient process in step 1, the expressions of each part of the clamping circuit are solved, and the transfer destination of the energy stored in the anode reactor is analyzed to obtain the expressions of the energy in each destination; according to the energy expression of the anode reactor fed back to the DC bus capacitor in the analysis results, within the allowable range of the maximum withstand voltage of the device, the clamping capacitor parameters are adjusted and optimized to maximize the energy fed back to the DC bus by the anode reactor, so as to achieve the purpose of improving the efficiency of the clamping circuit.

2. According to the high-power IGCT converter clamping circuit optimization design method described in claim 1, it is characterized in that: The clamping circuit topology of the IGCT converter is: Including DC bus capacitor C DC , DC bus capacitor C DC With anode reactor L i , IGCT converter, load inductor L Load To form a loop, clamping diode D CL and clamping capacitors C CL Then connect in series to the IGCT converter and load inductor in parallel L Load Both ends, clamp resistor R CL Connect the DC bus capacitors at both ends C DC With anode reactor L i , clamping diode D CL and clamping capacitors C CL The middle connection point of the load inductance L Load A fast recovery diode FWD is connected in parallel at both ends.

3. According to the high-power IGCT converter clamping circuit optimization design method described in claim 2, it is characterized in that: The two ends of the IGCT converter are connected in parallel with an anti-reverse diode D1.

4. A high-power IGCT converter clamping circuit optimization design method according to claim 2, characterized in that: In the clamping circuit of the IGCT converter, u Li (t) and i Li (t) represents the anode reactor L i The instantaneous voltage and instantaneous current at both ends, U CCL (t) and i CCL (t) represents the clamping capacitance C CL The instantaneous voltage and instantaneous current at both ends, U CDC and U T Represent the voltage across the DC capacitor and IGCT respectively, V D represents the steady-state voltage across the DC capacitor, i R (t) and I L Respectively represent the clamping resistance R CL and load inductance L Load of current.

5. A high-power IGCT converter clamping circuit optimization design method according to claim 4, characterized in that: The analysis process of the IGCT converter switching transient process in step 1 is as follows: In the transient process of breaking: IGCT is turned on, fast recovery diode FWD is turned off, and reverse recovery current is generated I rr ; At this time, the anode reactor L i The peak current passing through the IGCT is the load current I L The reverse recovery current of the fast recovery diode FWD I rr The sum of the anode reactor over time L i Current on i Li (t) Gradually reduce to load current I L ; In the shutdown transient state: ICGT is turned off, the fast recovery diode FWD is turned on, and the load inductance L Load Load current on I L The anode reactor is consumed in the closed loop composed of the load inductor and the fast recovery diode FWD. L i Current on i Li (t) From load current I L Finally, it drops to 0. Since the IGCT is turned off during this process, the anode reactor L i All the electrical energy on the capacitor is transferred through the clamping circuit.

6. A high-power IGCT converter clamping circuit optimization design method according to claim 5, characterized in that: In the step 2, the quantitative analysis process of the IGCT switching transient process in step 1 specifically includes: Since the IGCT's on-off transient time is much smaller than the circuit time constant, it is assumed in the analysis that the IGCT and the anti-parallel diode are turned on and off instantly; when the IGCT is turned on, the fast recovery diode FWD is turned off, generating a reverse recovery current. I rr ; At this time, the anode reactor L i The peak current passing through the IGCT is the load current I L The reverse recovery current of the fast recovery diode FWD I rr Therefore, the maximum energy stored in the anode reactor during a switching cycle is: ；(1) As time goes by, the anode reactor L i Current i Li (t) Gradually reduce to load current I L , so during the switching process, the energy dissipated by the anode reactor is: ；(2) In the turn-off transient state: ICGT is turned off, and the fast recovery diode FWD is turned on, and the load inductance L Load Load current on I L The anode reactor is consumed in the closed loop composed of the load reactance and the fast recovery diode FWD. L i Current on i Li (t) From load current I L Finally it drops to 0. Therefore, when the IGCT is turned off, the anode reactor L i The dissipated energy is: ； (3) Since the IGCT is in the off state during this process, the anode reactor L i All the electric energy on the anode reactor is transferred through the clamping circuit; from formulas (2) and (3), it can be seen that in one switching cycle, the anode reactor L i The total dissipated energy is given by equation (1), the anode reactor L i The energy dissipated in one cycle is proportional to the square of the sum of the load current and the reverse recovery current, which limits the efficiency improvement of the circuit. Therefore, it is necessary to analyze the anode reactor. L i The transfer of energy on the DC bus allows more energy to be fed back to the DC bus capacitor. C DC superior.

7. A high-power IGCT converter clamping circuit optimization design method according to claim 6, characterized in that: In the step 2, the parsing process of the expressions of each part of the clamping circuit is: The IGCT turn-off transient process is analyzed and deduced by formulas (1)-(3). The clamping capacitor U CCL The expression of (t) is: ；(4) Where D is the damping coefficient, ω 0 is the natural frequency: ；(5) During the IGCT turn-off transient process, the IGCT terminal voltage depends on the voltage across the clamping capacitor. To facilitate analysis and calculation, it is necessary to simplify the voltage expression across the clamping capacitor. Substituting the damping coefficient and the natural frequency into equation (4), the voltage expression is a sinusoidal amplitude attenuation waveform, which can be simplified using an approximate triangle average value: ；(6) Theoretical analysis and derivation of the IGCT turn-off transient process, DC bus capacitor C DC Voltage across the terminals U CDC The terminal voltage at (t) is: ；(7)。 8. A high-power IGCT converter clamping circuit optimization design method according to claim 7, characterized in that: In step 2, there are formulas (4)-(7) and the anode reactor is L i The reasoning process for where the stored energy is transferred is: When the shutdown transient is complete, the DC bus capacitor C DC The stored energy is: ； (8) According to equation (8), during the shutdown process, the anode reactor L i Transfer to DC bus capacitor C DC The energy on is: ；(9)。 9. A high-power IGCT converter clamping circuit optimization design method according to claim 8, characterized in that: In the step 2, the transient process of IGCT opening is theoretically analyzed and derived, and the DC bus capacitance can be obtained by solving the second-order circuit. C DC Peak voltage across the terminals U CDC (t) max The terminal voltage is as follows: ； (10) According to formula (10), during the opening process, the anode reactor L i Transfer to DC bus capacitor C DC The energy on is: ；(11)。 10. A high-power IGCT converter clamping circuit optimization design method according to claim 9, characterized in that: In the step 2, according to the anode reactor in formula (11): L i Feedback to DC bus capacitor C DC The energy expression on the anode reactor is constant by adjusting the clamping capacitor. C CL Parameters, can increase the anode reactor L i Feedback to DC bus capacitor C DC The energy on the device; within the maximum withstand voltage range of the device, the clamping capacitance can be reduced C CL Capacitance, making the anode reactor L i The energy fed back to the DC bus is maximized, thereby improving the efficiency of the clamping circuit.

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