A main circuit topology and measurement method for semiconductor on-state voltage drop test under pulsed high current conditions

Abstract

The present invention discloses a main circuit topology for testing the on-state voltage drop of semiconductors under pulsed high-current conditions. The circuit comprises a low-voltage turn-on circuit and a pulsed high-current freewheeling circuit. The low-voltage turn-on circuit is composed of a low-voltage capacitor C and a resistor R, while the pulsed high-current freewheeling circuit is composed of a high-voltage capacitor C0, a control switch S0, an inductor L0, and a diode D0. The present invention also discloses a measurement method for the test semiconductor. The semiconductor under test is not subjected to high voltage during the entire measurement process, and can be measured using a small-range low-voltage sensor, ensuring measurement accuracy. The present invention solves the difficult problem of measuring the on-state voltage drop of semiconductors under pulsed high-current conditions and can be used to guide the design of semiconductor branches in hybrid circuit breakers to ensure successful short-circuit interruption.

Description

Technical Field

[0001] The present invention belongs to the technical field of circuit breakers, and in particular relates to a main circuit topology for testing a semiconductor on-state voltage drop under a pulsed high current working condition, and a measurement method thereof. Background Art

[0002] Hybrid circuit breakers combine the low conduction losses of mechanical switches with the arc-free shutdown characteristics of semiconductor switches. They are an ideal topology for fault protection in large-capacity DC power systems and a key development direction for medium / high-voltage DC circuit breakers. The main circuit topology of a hybrid circuit breaker is shown in Figure 1, comprising a mechanical switch branch, a semiconductor branch, and a voltage-limiting and energy-dissipating branch. The semiconductor devices in the semiconductor branch of a hybrid circuit breaker can be categorized as either semi-controlled devices (such as thyristors) or fully controlled devices (such as GTOs, IGBTs, and IGETs). Regardless of the type of semiconductor device, when a short-circuit fault occurs, the first step in hybrid circuit breaking is to transfer the fault current from the mechanical switch branch to the semiconductor branch.

[0003] After a short-circuit fault occurs, the mechanical switch opens, and the arc voltage causes the fault current to transfer from the mechanical switch branch to the semiconductor branch. Because the arc voltage generated by the mechanical switch opening is low, the on-state voltage drop of the semiconductor under high-current pulse conditions becomes a key factor affecting current transfer and a crucial parameter in the design of hybrid circuit breakers. This parameter directly determines whether the fault current can be successfully transferred, especially as power system voltage levels increase and the number of series-connected semiconductor devices in hybrid circuit breakers increases.

[0004] Initially, when designing the semiconductor branches of hybrid circuit breakers, it was customary to reference the on-state voltage drop data provided by the manufacturer under steady-state current conditions. However, during application, it was found that the on-state voltage drop of the semiconductor was much higher than this value, resulting in frequent commutation failures, especially in medium / high voltage hybrid circuit breakers. Later, in order to obtain the semiconductor on-state voltage drop under pulsed high current conditions, it was proposed to use an LC circuit for measurement, such as Figure 2 As shown. When the capacitor C2 is fully charged, the switch S2 and the semiconductor under test T are turned on at the same time, and the C2-L2-S2-T loop is turned on, generating a pulse current. L To avoid the influence of (di / dt), only the voltage value at the peak of the pulse current is taken for each measurement as the on-state voltage drop at that current level. This measurement method has the following problems:

[0005] 1) Each measurement can only obtain the corresponding on-state voltage drop of a single-point current, and it is necessary to repeatedly adjust the loop parameters to obtain the corresponding on-state voltage drop.

[0006] Performing multiple measurements is too cumbersome;

[0007] 2) Voltage sensors have a time delay. The voltage at the peak current moment often lags behind, and the measured data cannot eliminate the influence of L (di / dt), making accuracy difficult to guarantee.

[0008] 3) Even when conducting currents in the tens of kA range, the on-state voltage drop across a semiconductor is only a few volts, necessitating the use of a low-voltage sensor for measurement. This requires that high voltages must not appear across the semiconductor under test throughout the entire test process, as this would damage the low-voltage sensor. In the measurement scheme shown, switch S2 carries the high voltage across capacitor C2 before the test. However, during the turn-on process, if switch S2 opens faster than the semiconductor under test, T, a high voltage will develop across the semiconductor under test. This has previously resulted in breakdown of the low-voltage sensor. Summary of the Invention

[0009] In view of the shortcomings of the existing technology, one of the purposes of the present invention is to provide a main circuit topology for testing the on-state voltage drop of semiconductors under pulsed large current conditions in response to actual application needs. The accurate measurement of the on-state voltage drop of semiconductors under pulsed large current conditions can be achieved without repeatedly adjusting the loop parameters. At the same time, "small range measurement of small voltage" is realized to ensure the accuracy of the measurement, provide accurate parameter guidance for the design of semiconductor branches of hybrid circuit breakers, and ensure the success of hybrid disconnection.

[0010] The technical solution adopted by the present invention to solve its technical problems is: a main circuit topology for semiconductor on-state voltage drop testing under pulsed high current working conditions, including a low-voltage turn-on circuit and a pulsed high-current freewheeling circuit; the low-voltage turn-on circuit is composed of a low-voltage capacitor C and a resistor R connected in series, and the pulsed high-current freewheeling circuit is formed by a high-voltage capacitor C0 and a control switch S0 connected in series with a diode D0 in parallel and then connected in series with an inductor L0; the low-voltage turn-on circuit and the pulsed high-current freewheeling circuit are connected to nodes Q1 and Q2 through a semiconductor to be tested T, and node Q2 is grounded, thereby forming a test loop with node Q1; the resistor R, the off-state resistance R1 of the semiconductor to be tested T and the resistance R of the control switch S0 are connected in parallel. S0 Satisfy R S0 >>R1>>R, the charging voltage of the low-voltage capacitor C is lower than the measuring range of the semiconductor voltage sensor T to be measured.

[0011] A second object of the present invention is to provide a method for measuring the main circuit topology of a semiconductor on-state voltage drop test under pulsed high current conditions, comprising the following steps:

[0012] (1) Connect the semiconductor T to be tested and the low-voltage sensor to the test circuit through nodes Q1 and Q2, and charge the low-voltage capacitor C and the high-voltage capacitor C0 to the expected voltage;

[0013] (2) The semiconductor T to be tested is triggered, the CRT low voltage turns on the circuit and the semiconductor T to be tested is turned on under low voltage and low current conditions, and the resistance changes from off-state resistance to on-state resistance;

[0014] (3) Delay Δ t After the semiconductor T to be tested is fully turned on, the control switch S0 is closed and the pulse large current freewheeling circuit is put into operation, entering the first stage: the C0-S0-L0-T loop is turned on, and the pulse large current begins to be injected into the semiconductor T to be tested. The low-voltage sensor measures the voltage value U 测 =U+L(di / dt), where U represents the actual on-state voltage drop of the semiconductor T to be measured, and L(di / dt) represents the induced electromotive force generated on the stray inductance of the semiconductor T to be measured due to the current change. The pulse current rise rate at this stage is extremely high, usually at the level of hundreds of A / μs, and a large induced electromotive force will be generated at both ends of the semiconductor device to be measured. 测 It cannot correctly reflect the semiconductor on-state voltage drop;

[0015] (4) As the voltage across the high-voltage capacitor C0 decreases until it crosses zero, the L0-T-D0 loop conducts and enters the second stage: the semiconductor T to be tested begins to flow continuously. At this time, the current change rate is extremely low, and L (di / dt) drops to the mV level, which is much smaller than the actual on-state voltage drop U of the semiconductor T to be tested. The low-voltage sensor measured voltage value U obtained in this stage is 测 It can more accurately reflect the on-state voltage drop of the semiconductor T to be tested at this current level.

[0016] The beneficial effects of the present invention are as follows: by controlling the conduction sequence of the low-voltage turn-on circuit and the pulse high-current freewheeling circuit, it is ensured that the semiconductor is not subjected to high voltage during the on-state voltage drop measurement process under the pulse high-current working condition, realizing "small range measurement of small voltage" and ensuring the accuracy of the measurement. At the same time, the introduction of the freewheeling process basically eliminates the influence of the induced electromotive force. There is no need to repeatedly adjust the parameters, and the on-state voltage drop corresponding to the current under the pulse high-current working condition can be measured at one time, which can provide relatively accurate parameter guidance for the design of the semiconductor branch of the hybrid circuit breaker and ensure the success of the hybrid disconnection. At the same time, it can be promoted and applied to the field of pulse power technology that has relatively strict requirements on the on-state voltage drop of semiconductors, and perform device selection, component design, and loss calculation, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the main circuit topology of hybrid circuit breaker;

[0018] Figure 2 Existing semiconductor on-state voltage drop test solution under pulsed high current conditions;

[0019] Figure 3 The main circuit topology of the present invention;

[0020] Figure 4This is the low voltage turn-on circuit topology of the present invention;

[0021] Figure 5 It is a pulse high current injection loop of the pulse high current freewheeling circuit of the present invention;

[0022] Figure 6 It is a pulse high current freewheeling loop of the pulse high current freewheeling circuit of the present invention;

[0023] Figure 7 The voltage and current waveforms when the semiconductor on-state voltage drop is measured using the present invention are shown. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to the accompanying drawings.

[0025] Reference Figure 3 As shown in the figure, the present invention discloses a main circuit topology for testing semiconductor on-state voltage drop under pulsed high-current conditions. The circuit comprises a low-voltage turn-on circuit and a pulsed high-current freewheeling circuit. The low-voltage turn-on circuit consists of a low-voltage capacitor C and a resistor R. The pulsed high-current freewheeling circuit consists of a high-voltage capacitor C0, a control switch S0, an inductor L0, and a diode D0. The semiconductor under test (including thyristors, GTOs, IGBTs, and IGETs) is connected to the test circuit via nodes Q1 and Q2.

[0026] The resistance value of the resistor R satisfies R S0 >>R1>>R, where R1 represents the off-state resistance of the semiconductor to be measured, R S0 Represents the resistance of control switch S0. The charging voltage of low-voltage capacitor C in the low-voltage turn-on circuit is less than the measuring range of the semiconductor voltage sensor under test. The charging voltage of high-voltage capacitor C0 in the pulsed high-current freewheeling circuit is relatively high, exceeding the kV level. This allows for the expected pulse current peak value while reducing the overall measurement device size.

[0027] During the test process, by controlling the conduction sequence of the low-voltage turn-on circuit and the pulse high-current freewheeling circuit, it is ensured that the semiconductor under test is not subjected to high voltage during the entire test process. It can be directly measured using a small-range low-voltage sensor, realizing "small-range measurement of small voltage" and ensuring measurement accuracy.

[0028] The present invention also discloses a method for testing the main circuit topology of a semiconductor on-state voltage drop test under a pulsed high current working condition, which includes the following steps.

[0029] 1) Connect the semiconductor under test (T) and the low-voltage sensor to the test circuit via nodes Q1 and Q2. Charge the low-voltage capacitor (C) and the high-voltage capacitor (C0) to the desired voltage. Based on the resistance relationship, the high voltage on the high-voltage capacitor (C0) is primarily borne by the control switch (S0). The voltage on the low-voltage capacitor (C) is primarily borne by the semiconductor under test (T).

[0030] 2) Reference Figure 7 As shown, at t=0, the semiconductor T to be tested is triggered, the CRT low voltage turns on the circuit and the semiconductor T to be tested is turned on under low voltage and low current conditions, and the resistance changes from off-state resistance to on-state resistance. The current direction is as follows Figure 4 shown.

[0031] 3) Reference Figure 7 As shown in the figure, at time t=t1, the semiconductor under test T is fully turned on. At this time, the control switch S0 is closed, and the pulsed high current freewheeling circuit is put into operation. Entering the first stage, the C0-S0-L0-T loop is turned on, and the pulsed high current begins to be injected into the semiconductor under test T. It is obvious that the voltage measured at both ends of the voltage sensor is very high. This is due to the induced electromotive force generated by the current change on the stray inductance of the semiconductor under test T. The direction of the current is as follows Figure 5 shown.

[0032] 4) Reference Figure 7 As shown in the figure, at t=t2, as the voltage across the high-voltage capacitor C0 crosses zero, the L0-T-D0 loop is turned on, and the second phase begins. The semiconductor under test T begins to flow continuously. The voltage sensor reading drops significantly. In this phase, (di / dt) max ≈1A / μs, the stray inductance is about 0.02μH, then L(di / dt)≤0.02V, which is much smaller than (di / dt) max The on-state voltage drop at the corresponding moment is 5.74V, which can be ignored. Therefore, it can be considered that the voltage sensor reading at this stage can more accurately reflect the on-state voltage drop of the semiconductor under test at this current level. Figure 6 shown.

[0033] It can be seen that the present invention solves the problem of measuring the on-state voltage drop of semiconductors under pulsed high current conditions. By controlling the conduction sequence of the low-voltage turn-on circuit and the pulsed high current freewheeling circuit, it is ensured that the semiconductor is not subjected to high voltage during the on-state voltage drop measurement process under pulsed high current conditions, realizing "small range to measure small voltage" and ensuring the accuracy of the measurement. At the same time, the introduction of the freewheeling process basically eliminates the influence of the induced electromotive force. There is no need to repeatedly adjust the parameters, and the on-state voltage drop corresponding to all currents under the corresponding pulsed high current conditions can be measured at one time, which can provide relatively accurate parameter guidance for the design of semiconductor branches of hybrid circuit breakers and ensure the success of hybrid disconnection.

[0034] The above embodiments are merely illustrative of the principles, effects and specific implementation methods of the present invention. Within the technical scope of the art, without departing from the concept of the present invention, several modifications and improvements made to the topology of the present invention fall within the scope of protection of the present invention.

Claims

1. A method for measuring the main circuit topology of a semiconductor on-state voltage drop test under pulsed high current conditions, characterized in that: The main circuit topology includes a low-voltage turn-on circuit and a pulse high-current freewheeling circuit; the low-voltage turn-on circuit is composed of a low-voltage capacitor C and a resistor R in series, and the pulse high-current freewheeling circuit is formed by a high-voltage capacitor C0 and a control switch S0 connected in series with a diode D0 in parallel and then connected in series with an inductor L0. The low-voltage turn-on circuit and the pulse high-current freewheeling circuit are connected to nodes Q1 and Q2 through the semiconductor to be tested T, and the node Q2 is grounded, thereby forming a test loop with the node Q1; the resistor R, the off-state resistance R1 of the semiconductor to be tested T and the resistance R of the control switch S0 are connected in parallel. S0 Satisfy R S0 >>R1>>R, the charging voltage of the low-voltage capacitor C is lower than the measuring range of the semiconductor voltage sensor T to be measured; the following steps are included: (1) Connect the semiconductor T to be tested and the low-voltage sensor to the test circuit through nodes Q1 and Q2, and charge the low-voltage capacitor C and the high-voltage capacitor C0 to the expected voltage; (2) The semiconductor T to be tested is triggered, the CRT low voltage turns on the circuit and the semiconductor T to be tested is turned on under low voltage and low current conditions, and the resistance changes from off-state resistance to on-state resistance; (3) After the semiconductor T to be tested is fully turned on, the control switch S0 is closed, and the pulse large current freewheeling circuit is put into operation, entering the first stage: the C0-S0-L0-T loop is turned on, and the pulse large current begins to be injected into the semiconductor T to be tested, and the low-voltage sensor measures the voltage value U 测 =U+L(di / dt), where U represents the actual on-state voltage drop of the semiconductor T to be measured, and L(di / dt) represents the induced electromotive force generated on the stray inductance of the semiconductor T to be measured due to the current change; (4) As the voltage across the high-voltage capacitor C0 decreases until it crosses zero, the L0-T-D0 loop is turned on and enters the second stage: the semiconductor T to be tested begins to flow and obtain the voltage value U measured by the low-voltage sensor 测 .

Images