JP6803121B2 - Power converter - Google Patents

Description

An embodiment of the present invention relates to a power conversion device capable of preventing damage to an element due to heat.

A power converter that converts direct current to alternating current, alternating current to direct current, direct current to direct current, or alternating current to alternating current utilizes the switching action of a power semiconductor element. For example, a power converter includes a thyristor valve in which a large number of thyristors are connected in series. A snubber circuit is provided in parallel with each thyristor constituting the thyristor valve. The snubber circuit consists of a series circuit of a capacitor and a resistor, and suppresses the spike-like high voltage generated during on / off switching of the thyristor to prevent damage to the thyristor.

Since a power semiconductor element such as a thyristor may be damaged by heat generated due to loss, a cooling device is provided. However, since heat generation exceeding the cooling capacity may occur, the power conversion device estimates the temperature of the semiconductor element, and when the estimated temperature exceeds the threshold value, a process such as stopping the device is performed.

Japanese Unexamined Patent Publication No. 2005-124387

The conventional power conversion device does not estimate the temperature of the element from the data representing the operating condition during the operation of the device. Further, the resistance of the peripheral circuit such as the snubber circuit also generates heat, but the conventional power conversion device does not consider the temperature of the resistance.

An object of the present invention is to provide a power conversion device capable of detecting a temperature rise that may cause damage to an element during operation and preventing damage to the element.

According to one aspect of the present invention, the power converter calculates and calculates the temperature based on the output of the thyristor converter, the sensor means for detecting the state data indicating the operating state of the thyristor converter, and the output of the sensor means. It is provided with a control means for controlling the thyristor converter according to the temperature. The thyristor valve of the thyristor converter consists of multiple thyristors connected in series, multiple snubber resistors connected in parallel to each of the multiple thyristors, and multiple voltage dividing resistors connected in parallel to each of the multiple thyristors. , Equipped with. The control means calculates the element junction temperature of the thyristor, the resistance wire temperature of the snubber resistor, and the resistance wire temperature of the voltage dividing resistor. A plurality of heat sinks for cooling the plurality of thyristors, and a plurality of water cooling resistors constituting the plurality of snubber resistors and the plurality of voltage dividing resistors are further provided. The control means is based on the thermal resistance of the plurality of thyristors, the thermal resistance of the plurality of heat sinks, the element loss of the plurality of psyllistas, and the inlet temperature of the cooling water injected into the plurality of heat sinks. The element junction temperature of the plurality of thyristors is calculated, the thermal resistance of the plurality of snubber resistors, the loss caused by the plurality of snubber resistors, and the cooling injected into the plurality of water-cooled resistors constituting the plurality of snubber resistors. The resistance line temperature of the plurality of snubber resistors is calculated based on the ingress temperature of water, and the thermal resistance of the plurality of voltage dividing resistors, the loss caused by the plurality of voltage dividing resistors, and the plurality of voltage dividing resistors are calculated. The resistance line temperature of the plurality of voltage dividing resistors is calculated based on the inlet temperature of the cooling water injected into the plurality of water cooling resistors constituting the above. Each of the plurality of snubber resistors is divided into a first resistor and a second resistor. The plurality of water-cooled resistors include a plurality of first water-cooled resistors constituting the plurality of voltage dividing resistors and the first resistance of the plurality of snubber resistors, and a plurality of plurality of second resistors of the plurality of snubber resistors. It is equipped with a second water-cooled resistor. Each of the plurality of thyristor valves includes the plurality of first water-cooled resistors, the plurality of second water-cooled resistors, and the plurality of heat sinks. The plurality of heat sinks are connected in series with the plurality of first water-cooled resistors or the plurality of second water-cooled resistors. A series circuit of the plurality of heat sinks and the plurality of first water-cooled resistors or the plurality of second water-cooled resistors is arranged in parallel between the inlet side end portion of the cooling water and the outlet side end portion of the cooling water. Be placed.

According to the present invention, by estimating the temperature based on the data according to the operating condition during operation and controlling the operation of the thyristor according to the estimated temperature, it is possible to prevent the element from being damaged due to the temperature rise. A power converter can be provided.

FIG. 1 is a diagram showing an example of a power conversion device according to the first embodiment. FIG. 2 is a diagram showing an example of a thyristor valve of a reactive power compensating device constituting the power conversion device according to the first embodiment. FIG. 3 is a diagram showing an example of a voltage detector that detects forward voltage and reverse voltage in the first embodiment. FIG. 4 is a diagram showing an example of a voltage detector that detects a forward voltage according to the first embodiment. FIG. 5 is a diagram showing an example of the gate control device according to the first embodiment. FIG. 6 is a diagram showing an example of a cooling pipe provided in the power conversion device according to the first embodiment. FIG. 7 is a diagram showing an example of a cooling pipe provided in the power conversion device according to the second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a diagram showing an example of a power conversion device 10 according to the first embodiment of the present invention.

The power conversion device 6 includes a reactive power compensation device 8, a gate control device 10, a sensor group 12, and a control panel 14. The reactive power compensator 8 is connected to the gate control device 10 by an optical fiber cable or the like (not shown). The reactive power compensator 8 has a function of converting three-phase AC power supplied from the three-phase AC power supply 2 into DC power (also referred to as rectification) and reactive power of the three-phase AC power supplied from the three-phase AC power supply 2. Has the function of compensating for. Here, it is assumed that the three-phase AC power is composed of U-phase, V-phase, and W-phase. The reactive power compensator 8 is a static reactive power compensator (SVC: static var compensator) that employs a thyristor controlled reactor (TCR) system. The reactive power compensating device 8 opens and closes the thyristor valves 8U, 8V, 8W, 8X, 8Y, and 8Z as AC switches, adjusts the current flowing through the reactors R1 to R6, and compensates for the reactive power.

The reactive power compensator 8 is configured by delta-connecting a UX phase circuit, a VY phase circuit, and a WZ phase circuit. The UX phase circuit compensates for reactive power between the UV phases of the power system. The VY phase circuit compensates for reactive power between the VW phases of the power system. The WZ phase circuit compensates for reactive power between the WU phases of the power system.

The UX phase circuit is composed of two thyristor valves 8U and 8X and two reactors R1 and R2. The thyristor valves 8U and 8X are connected in parallel in the direction in which the current flows in the opposite direction. The reactors R1 and R2 are connected in series with the thyristor valves 8U and 8X.

The VY phase circuit is composed of two thyristor valves 8V and 8Y and two reactors R3 and R4. The thyristor valves 8V and 8Y are connected in parallel in the direction in which the current flows in the opposite direction. The reactors R3 and R4 are connected in series with the thyristor valves 8V and 8Y.

The WZ phase circuit is composed of two thyristor valves 8W and 8Z and two reactors R5 and R6. The thyristor valves 8W and 8Z are connected in parallel in the direction in which the current flows in the opposite direction. The reactors R5 and R6 are connected in series with the thyristor valves 8W and 8Z.

The reactor R1 of the UX phase circuit and the reactor R6 of the WZ phase circuit are connected, and this connection point becomes the U phase terminal Ta connected to the U phase of the power system. The reactor R2 of the UX phase circuit and the reactor R3 of the VY phase circuit are connected, and this connection point becomes the V phase terminal Tb connected to the V phase of the power system. The reactor R5 of the WZ phase circuit and the reactor R4 of the VY phase circuit are connected, and this connection point becomes the W phase terminal Tc connected to the W phase of the power system.

FIG. 2 is a configuration diagram showing an example of the configuration of the thyristor valves 8U and 8X of the UX phase circuit according to the present embodiment. Since the thyristor valves 8V and 8Y; 8W and 8Z of the VY phase circuit and the WZ phase circuit are also configured in the same manner, the thyristor valves 8U and 8X of the UX phase circuit will be described here as representatives.

Thyristor valves 8U, 8X includes N pieces of thyristor ₂₀ 1 connected in series so that a current flows from the terminal Ta in the direction of the terminal Tb, ₂₀ 2, ... 20 _N (any thyristor will be referred to as a thyristor 20), N number of the thyristor ₂₁ a current from the terminal Tb in the direction of the terminal Ta is connected in series to flow 1, ₂₁ 2, ... 21 _N and (any thyristor will be referred to as a thyristor 21), the N snubber circuit 22 ₁ , _{22 2,} 22 3, ..., 22 _N (optional snubber circuit is referred to as a snubber circuit 22) and, N-number of voltage dividing resistors _{24 1, 24 2, 24 3} , ..., 24 N ( arbitrary partial pressure The resistor is referred to as a voltage dividing resistor 24) and N voltage detectors 26 ₁ , 26 ₂ , 26 ₃ , ..., 26 _N (any voltage detector is referred to as a voltage detector 26). N is an integer greater than or equal to 2.
The N thyristors 20 _{1 to} 20 _N and 21 _{1 to} 21 _N are all connected in series. The N thyristors 20 and the N thyristors 21 are connected in antiparallel to each other so as to correspond to each other. The N snubber circuits 22 are connected in parallel so as to correspond to each set of the N sets of thyristors 20 and 21 connected in antiparallel. The snubber circuit 22 has a configuration in which a capacitor 30 and a resistor 28 are connected in series. The N voltage dividing resistors 24 _{1 to} 24 _N are connected in series with the _N voltage detectors 26 _{1 to} 26 _N , respectively. _N circuits in which the voltage dividing resistors 24 _{1 to} 24 _N and the voltage detectors 26 _{1 to} 26 _N are connected in series are in parallel with _N thyristors 20 _{1 to} 20 _N and 21 _{1 to} 21 _N , respectively. Be connected.

The thyristors 20 and 21 are switching elements having a rectifying action. The thyristors 20 and 21 are driven (ignited) in response to the gate pulse GP supplied from the gate control device 10 via the optical fiber cable. By driving the thyristors 20 and 21, AC power is converted into DC power.

The voltage dividing resistors 24 _{1 to} 24 _N uniformly divide the DC voltage component applied between the poles of the thyristor valves 8U and 8X, and also serve to suppress the current flowing through the voltage detectors 26 _{1 to} 26 _N.

Snubber circuits ₂₂ 1 through 22 _N is a thyristor valve 8U, with pressure uniformity minute AC voltage component applied between 8X poles, each thyristor ₂₀ 1 _{to 20 N,} 21 thyristors ₂₀ 1 to 1 through 21 _N turn-on and during turn-off of the 20 _{N, 21} 1 through 21 thyristor ₂₀ 1 _{to 20} from a heterogeneous and overvoltage transient voltage sharing applied to _{N N,} protect the 21 1 through 21 _N. The snubber circuits 22 _{1 to} 22 _N are provided for thyristors 20 _{1 to} 20 _N and 21 _{1 to} 21 _N , respectively, in order to reduce power loss and enable stable switching. Each snubber circuit 22 _{1 to} 22 _N has a snubber resistor 28 _{1 to} 28 _N (any snubber resistor is referred to as a snubber resistor 28) and a capacitor 30 ₁ to 30 _N (any capacitor is referred to as a capacitor 30). It consists of a series connection circuit.

Voltage detector ₂₆ 1 ~ 26 _N are each thyristor _{20 1 ~20 N, 21 1 ~21} N to the forward voltage (the voltage of the thyristor _{20 1 ~20 N, 21 1 ~21} N current flows in a direction) is applied Then, the forward voltage signals FV _{1 to} FV _N are output to the gate control device 10, respectively. In this way, the voltage detectors 26 _{1 to} 26 _N detect the forward voltage.

Some of the voltage detector, for example, three voltage detectors ₂₆ 1 to 26 ₃ each thyristor ₂₀ 1 _{to 20 3,} 21 1 to 21 ₃ in the reverse voltage (polarity opposite voltage forward voltage) is applied Then, the reverse voltage signals RV _{1 to} RV ₃ are output to the gate control device 10, respectively. In this manner, the voltage detector ₂₆ 1-26 ₃ detects the reverse voltage. That is, three voltage detectors ₂₆ 1 to 26 ₃ detects both the forward voltage and the reverse voltage.

When the number of thyristors included in the thyristor valve is large, a plurality of thyristor modules may be connected in series to form the thyristor valve. In this case, each thyristor module consists of a plurality of thyristors connected in series, as shown in FIG.

The gate control device 10 generates a gate pulse GP based on various signals received from the control panel 14 and forward voltage signals FV _{1 to} FV _N or reverse voltage signals RV _{1 to} RV ₃ received from thyristor valves 8U and 8X. .. The gate control device 10 outputs the gate pulse GP to the thyristors 20 _{1 to} 20 _N and 21 _{1 to} 21 _N via an optical fiber cable to drive the thyristors 20 _{1 to} 20 _N and 21 _{1 to} 21 _N. .. As a result, the thyristor valves 8U and 8X perform a power conversion operation.

The sensor group 12 includes various sensors installed at various locations so as to detect the operating status of the thyristor valves 8U and 8X. The output of the sensor group 12 is input to the control panel 14. The control panel 14 calculates the element junction temperature of the thyristors 20 and 21, the resistance wire temperature of the snubber resistor 28, and the resistance wire temperature of the voltage dividing resistor 24. As an example, the sensor group 12 detects the inlet temperature of the cooling water, the valve voltage, the current flowing through the thyristor (element current), and the like as the operating conditions.

The control panel 14 is composed of, for example, a calculation unit 14a and a control unit 14b, but the calculation unit 14a and the control unit 14b may be integrally configured.

The calculation unit 14a calculates the element junction temperature of the thyristors 20 and 21, the resistance wire temperature of the snubber resistor 28, and the resistance wire temperature of the voltage dividing resistor 24 based on the operating conditions of the thyristor valves 8U and 8X which are the outputs of the sensor group 12. To do.

The control unit 14b transmits and receives various signals to and from the gate control device 10 to control and monitor the power conversion of the thyristor valves 8U and 8X. Further, the control unit 14b controls the operation of the thyristor valves 8U and 8X according to the calculation result by the calculation unit 14a.

For example, the element junction temperature of thyristors 20 _{1 to} 20 _N and 21 _{1 to} 21 _N calculated by the calculation unit 14a, the resistance wire temperature of the snubber resistance 28 _{1 to} 28 _N , and the resistance wire temperature of the voltage dividing resistance 24 _{1 to} 24 _N. When at least one of the above exceeds the threshold value, the control unit 14b sends a high temperature detection signal HT to the gate control device 10, and the gate pulse GP from the gate control device 10 to the thyristors 20 _{1 to} 20 _N and 21 _{1 to} 21 _N. The supply of thyristor valves 8U and 8X is stopped. Here, the threshold value of the element junction temperature of the thyristors 20 and 21, the threshold value of the resistance wire temperature of the snubber resistor 28, and the threshold value of the resistance wire temperature of the voltage dividing resistor 24 are not necessarily the same values.

It is sufficient that the gate control device 10 can prevent the element junction temperature of the thyristors 20 and 21, the resistance wire temperature of the snubber resistor 28, and the resistance wire temperature of the voltage dividing resistor 24 from rising, and the operation of the thyristor valves 8U and 8X can be stopped. Not limited to this, any control may be used. For example, a light load operation may be performed in which a gate pulse is continuously supplied to the gate of the thyristor so that a reverse voltage is not applied.

Figure 3 is a diagram showing an example of a voltage detector 26 ₁ configured to detect the forward voltage and reverse voltage. Here, also for the configuration of the voltage detector ₂₆ 2, 26 _3, is similar to the configuration of the voltage detector 26 _1, the description thereof is omitted.

The voltage detector 26 ₁ includes Zener diodes DZF and DZR, light emitting elements LF and LR, and a resistor RD.

Zener diode DZF is connected to the voltage dividing resistors 24 ₁ series. The Zener diode DZF is mounted in a direction that blocks the current flowing due to the forward voltage. Zener diode DZF, when forward voltage is applied to the voltage detector 26 ₁ to apply a voltage for causing the light emitting element LF. When the current due to the forward voltage becomes excessive (when an overcurrent flows), the Zener diode DZF conducts in the direction in which this current flows. As a result, the Zener diode DZF protects the light emitting element LF from an excessive current.

Emitting element LF, when forward voltage is applied to the voltage detector 26 _1, emits light. When the light emitting element LF emits light, the light emitting element LF outputs a forward voltage signal FV ₁ to the gate control device 10. The light emitting element LF is, for example, a light-emitting diode (LED).

The Zener diode DZR is connected in series with the Zener diode DZF in the opposite direction to the Zener diode DZF. That is, the Zener diode DZR is attached in a direction of blocking the current flowing due to the reverse voltage. Zener diode DZR, when reverse voltage is applied to the voltage detector 26 ₁ to apply a voltage for causing the light emitting element LR. When the current due to the reverse voltage becomes excessive (when an overcurrent flows), the Zener diode DZR conducts in the direction in which this current flows. As a result, the Zener diode DZR protects the light emitting element LR from overcurrent.

Emitting element LR, when reverse voltage is applied to the voltage detector 26 _1, emits light. When the light emitting element LR emits light, the light emitting element LR outputs a reverse voltage signal RV ₁ to the gate control device 10. The light emitting element LR is, for example, a light emitting diode.

The resistor RD suppresses the current flowing through the light emitting elements LF and LR. As a result, the resistor RD passes a predetermined current for causing light emission to the light emitting elements LF and LR.

Figure 4 is a diagram showing an example of the configuration of the voltage detector 26 ₄ for detecting the forward voltage. Here, also for the configuration of the voltage detector ₂₆ 5 ~ 26 _N, it is the same as the configuration of the voltage detector 26 _4, the description thereof is omitted.

Current detector 26 _4, the voltage detector 26 ₁ shown in FIG. 3, a configuration obtained by removing the zener diode DZR and the light emitting element LR.

The Zener diode DZF prevents a voltage having a polarity opposite to that of the light emitting element LF from being applied. Other points, the voltage detector 26 _4, the same configuration as that of the voltage detector 26 ₁ shown in FIG.

FIG. 5 is a diagram showing an example of the configuration of the gate control device 10.

The gate control device 10 includes a majority decision circuit 42, a thyristor failure detection circuit 44, and a gate control circuit 46.

Majority circuit 42 receives a reverse voltage signal _RV 1 _{~RV 3} output from the three voltage detector ₂₆ 1-26 _3. The majority decision circuit 42 outputs the calculation results of the received reverse voltage signals RV _{1 to} RV ₃ as the reverse voltage signal RV to the thyristor failure detection circuit 44 and the gate control circuit 46. When the majority decision circuit 42 receives two or more reverse voltage signals RV _{1 to} RV ₃ , the reverse voltage signal RV is set to "1" and output. When the majority decision circuit 42 receives one or less reverse voltage signals RV _{1 to} RV ₃ , the reverse voltage signal RV is set to "0" and output. That is, when receiving the reverse voltage signal from the voltage detector 26 _{1-26 3} majority (number of more than one-half), the majority circuit 42 outputs a reverse voltage signal RV which indicates "1". If not, the majority circuit 42 outputs a reverse voltage signal RV indicating "0".

The thyristor failure detection circuit 44 receives the forward voltage signals FV _{1 to} FV _N output from the voltage detectors 26 _{1 to} 26 _N and the reverse voltage signal RV output from the majority decision circuit 44, respectively. The thyristor failure detection circuit 44 is based on the forward voltage signals FV _{1 to} FV _N and the reverse voltage signal RV, and the failure detection signals NG _{1 of the} thyristor valves 8U and 8X of the thyristors 20 _{1 to} 20 _N and 21 _{1 to} 21 _N , respectively. ~ NG _N is detected. The thyristor failure detection circuit 44 uses the forward voltage aggregate signal FV used to drive the thyristors 20 and 21 of the thyristor valves 8U and 8X as the gate control circuit 46 based on the forward voltage signals FV _{1 to} FV _N and the reverse voltage signal RV. Output to.

The gate control circuit 46 includes a phase control on-timing signal ON, which is a signal for conducting the thyristors 20 and 21, a gate block GB that suppresses the output of the gate pulse GP, a phase control on-timing signal TON of another phase that commutates, and a thyristor. The forward voltage aggregation signal FV output from the element failure detection circuit 22, the reverse voltage signal RV output from the majority decision circuit 42, and the high temperature detection signal HT from the control unit 14b of the control panel 14 are input.

The gate control circuit 46 generates a gate pulse GP based on the phase control on-timing signal ON and the forward voltage aggregation signal FV. The gate control circuit 46 outputs the generated gate pulse GP to the thyristors 20 _{1 to} 20 _N and 21 _{1 to} 21 _N of the thyristor valve 8U. As a result, the gate control circuit 46 ignites the thyristors 20 _{1 to} 20 _N and 21 _{1 to} 21 _N , respectively. When the gate control circuit 46 detects a commutation failure of the thyristor valves 8U and 8X after outputting the gate pulse GP, it outputs a commutation failure signal CFD. The gate control circuit 46 stops the output of the gate pulse GP based on the gate block GB, the phase control on-timing signal TON of the commuting other phase, and the reverse voltage signal RV. Further, the gate control circuit 46 stops the operation of the thyristor valves 8U and 8X in response to the high temperature detection signal HT from the control unit 14b, or supplies a gate pulse to the gate of the thyristor so that a reverse voltage is not applied. Continue light load operation. The power conversion device 6 includes a cooling device for processing heat generated by loss of elements such as thyristors 20, 21, resistors 24, and 28 constituting thyristor valves 8U and 8X. The thyristor is cooled by a heat sink. A water-cooled resistor is used as the resistors 24 and 28, and the resistance wire itself is cooled. The cooling medium includes air, water, CFC substitutes, and the like, and for example, water is used. FIG. 6 shows an example of a cooling water piping system included in the power conversion device 6. FIG. 6 shows the cooling water piping system of the thyristor valve 8U as an example. The piping system of the thyristor valves 8V, 8W, 8X, 8Y and 8Z has the same structure.
Heat sinks 62 _{1 to} 62 _{N + 1} (any heat sink is referred to as heat sink 62) are arranged on both sides of the thyristors 20 _{1 to} 20 _N. The heat sink _{62 1 ~62 N +} 1 of the water inlet is connected through a branch pipe to the cooling water inlet side header pipe 68, connected to the cooling Mizuide side main pipe 70 heat sink _{62 1 ~62 N +} 1 of the water outlet via the branch pipe Will be done.

The water injection port of the water-cooled resistors 64 ₁ to 64 _N (any water-cooled resistor is referred to as water-cooled resistor 64) constituting the snubber resistors 28 _{1 to} 28 _N is connected to the cooling water inlet side mother pipe 68 via a branch pipe. The outlets of the water cooling resistors 64 ₁ to 64 _N are connected to the cooling water outlet side mother pipe 70 via a branch pipe. The water injection port of the water-cooled resistors 66 _{1 to} 66 _N (any water-cooled resistor is referred to as the water-cooled resistor 66) constituting the voltage dividing resistors 24 _{1 to} 24 _N is the main pipe 68 on the cooling water inlet side via a branch pipe. The water outlets of the water cooling resistors 66 _{1 to} 66 _N are connected to the cooling water outlet side mother pipe 70 via a branch pipe. In this way, the heat sinks 62 _{1 to} 62 _{N + 1} , the water cooling resistors 64 ₁ to 64 _N , and the water cooling resistors 66 _{1 to} 66 _N are arranged in parallel between the cooling water inlet side master pipe 68 and the cooling water outlet side master pipe 70. Placed in. Therefore, the cooling water injected into the cooling water inlet side mother pipe 68 is injected in parallel with the heat sinks 62 _{1 to} 62 _{N + 1} , the water cooling resistors 64 ₁ to 64 _N , and the water cooling resistors 66 _{1 to} 66 _N. Cooling water discharged from each of the heat sinks 62 _{1 to} 62 _{N + 1} , the water cooling resistors 64 ₁ to 64 _N , and the water cooling resistors 66 _{1 to} 66 _N is supplied to a cooling unit (not shown) via the cooling water outlet side mother pipe 70. To. The cooling water cooled by the cooling unit is supplied to the cooling water inlet side mother pipe 68, and the cooling water is circulated.

Next, in order to prevent the thyristor 20 and the resistors 64 and 66 from being destroyed, the element junction temperature of the thyristor 20 and the resistance wire temperature of the resistors 64 and 66 (or the resistors 28 and 24) are estimated from the operating conditions of the thyristor valve 8U. , The operation to monitor is explained.

(1) Calculation of element junction temperature of thyristor 20
The calculation unit 14a calculates the element junction temperature _Tvj of the thyristor 20 by the following formula based on the data acquired from the sensor group 12.
T _vj = (R _thy + R _fin ) P _thy + T _tin (1)
Here, T _tin is the entry temperature (° C.) of the cooling water detected by the sensor installed at the water injection port of the heat sinks 62 _{1 to} 62 _{N + 1} adjacent to each thyristor.

_Also, thermal resistance of _{R thy} thyristor _{20, R fin} is the thermal resistance of the heat sink 62, expressed by the following equations, respectively. R _nt is the thermal resistance of the thyristor, R _fn is the thermal resistance of the heat sink, and τ _nt and τ _fn are time constants. The unit of thermal resistance is K / W.

However, these thermal resistances are constants determined for each product, and the constants may be used without actually calculating using the equations (2) and (3).

_{Pthy in} equation (1) is element loss. This element loss is calculated by the following equation using the energization loss P _cnd , the turn-on loss P _swon , and the turn-off loss P _swof in the thyristor.

P _thy = P _cnd + P _swon + P _swof (4)
Here, P _cnd , P _swon , and P _swof are calculated by the following equations, respectively.

P _cnd = U _to x I _TAV + R _to x I ² _TRMS (5)
P _swon = 0.02P _cnd (di / dt ≤ 2 A / μs) (6)
= 0.035P _cnd (di / dt> 2 A / μus)

(5) _{U to} the formula threshold voltage _{(V), I TAV} is the average current _{(A), R to} the slope resistance _{(Ω), I TRMS} is the effective value current (A). Threshold voltage _U-to, the slope resistance _R-to is known, the average current _{I TAV,} the effective value current _{I TRMS} is detected by a current sensor connected in series to the thyristor. In equation (6), di / dt is the time derivative of the element current. (7) _{Q rr} reverse recovery charge in the formula (μQ), _{V S} is the valve voltage (V), alpha is the control angle (°), f is the frequency (Hz), N is the serial number of the thyristor. Serial number of thyristors N, reverse recovery charge Q _rr, the control angle alpha, the frequency f is known and the valve voltage V _S is detected by the voltage detector 26.

Calculation unit 14a calculates the element junction temperature _{T vj} thyristor 20 to 20 _N on the basis of the equation (1).

The element loss _Pthy can be _calculated by the following equation instead of the equation (4).

_{P thy = (U t + R} t × I thy) × I thy (8)
Here, I _thy is the current flowing through the thyristor (device current) (A), U _t is selected the threshold voltage to match the actual element loss (V), R _t is to match the actual element Loss The selected slope resistance (Ω). The threshold voltage _Ut and the slope resistance _Rt are known to be selected so that the calculation results of equations (5) to (7) are substituted into equations (4) and the calculation results of equation (8) match. It is a value, and the element current I _thy is detected by a sensor installed in the thyristor.

If equation (8) is used for the calculation of the element loss _Pthy , less data is required for the calculation than when equations (4) to (7) are used.
(2) Calculation of resistance wire temperature of resistors 64 and 66
The calculation unit 14a calculates the resistance line temperature _Tr of the resistors 64 and 66 _{N by} the following formula based on the data acquired from the sensor group 12. _{T r = R r · P r} + T rin (9)
Here, _Trin is the temperature of the cooling water detected by the sensors installed at the water inlets of the resistors 64 and 66.

R _r is the thermal resistance of the resistors 64 and 66 and can be expressed by the following equation. The unit of thermal resistance is K / W.

P _r is that losses resulting resistance line, when calculating the temperature of the snubber resistor 64, the loss of snubber resistor (snubber loss) when the P _snb, calculating the temperature of the voltage dividing resistors 66 The _{voltage dividing} resistance loss _Pvd is used for this.

However, the thermal resistance R _{r is} also a constant determined for each product, and the constant is actually used without being calculated using the equation (10).

The snubber loss P _snb and the partial pressure loss P _vd can be expressed by the following equations, respectively.

f is the _frequency, the _{C snb} capacitance of the capacitor of the snubber circuit, the _{V S} valve voltage, N is the number of series of snubber _{circuits, R vd} is dividing resistors (Omega). Frequency f, the capacitance of the capacitor of the snubber circuit C _snb, serial number N of the snubber circuit is known, the valve voltage V _S is detected by a sensor installed in a thyristor bubble. Calculation unit 14a calculates the resistance wire temperature _{T r} of (9) ₆₄ 1 ~64 N resistors based on _formula, 66 1 -66 _N.
The temperature calculated by the calculation unit 14a is supplied to the control unit 14b. The control unit 14b is at least _one of the element junction temperature of the thyristor 20 _{1 to} 20 _N , the resistance wire temperature of the snubber resistance 28 _{1 to} 28 _N , and the resistance wire temperature of the voltage dividing resistance 24 _{1 to} 24 _N calculated by the calculation unit 14a. When the temperature exceeds the threshold value, the operation of the thyristor valve 8U is controlled so that the generation of heat is reduced. For example, the operation of the thyristor valve 8U is stopped, or a light load operation is performed in which the gate pulse is continuously supplied to the gates of the thyristors 20 _{1 to} 20 _N so that the reverse voltage is not applied. Various characteristics of the thyristor, such as turn-off time and withstand voltage, depend on the temperature of the thyristor, and when the temperature exceeds a predetermined value, the design performance cannot be maintained. The calorific value of the thyristor depends on its energizing current, and when the temperature exceeds the threshold value due to overload or the like, it is necessary to quickly reduce the energizing current.

As described above, according to the embodiment, the element junction temperature and the resistance wire temperature can be calculated based on the data representing the operating state during the operation of the thyristor valve 8U, and the temperature rise can be monitored. Therefore, when the temperature exceeds the threshold value, the operation can be controlled and damage to the thyristor and the resistor can be prevented. The temperature calculation is not limited to the equations (1) and (9), and other similar equations may be used.
[Second Embodiment]
In the first embodiment, a cooling pipe in which a heat sink and a water cooling resistor are connected in parallel was used. The calculation of temperature depends on the path of the cooling pipe. A second embodiment using a cooling pipe having a route different from that of FIG. 6 will be described. In the second embodiment, as shown in FIG. 7, the heat sink and the water cooling resistor are connected in series.

FIG. 7 shows a cooling pipe for a portion that cools the two thyristor valves 8U and 8X. Since the thyristor valves 8V and 8Y and the thyristor valves 8W and 8Z are the same as the thyristor valves 8U and 8X, they are not shown.

In the thyristor valve 8U, heat sinks 62 _{1 to} 62 _{N + 1} are arranged on both sides of the thyristor 20 _{1 to} 20 _N , as in the embodiment of FIG. The heat sink _{62 1 ~62 N +} 1 of the water inlet is connected through a branch pipe to the cooling water inlet side header pipe 68, the heat sink _{62 1 ~62 N +} 1 of the water outlet is connected to a water cooled resistor _{72 1 ~72 N +} 1 of the water inlet To. The water outlets of the water cooling resistors 72 _{1 to} 72 _{N + 1} are connected to the cooling water outlet side mother pipe 70 via a branch pipe. Not all water-cooled resistors 72 have the same resistance value, but every other one has a different resistance value. Odd water cooled resistor ₇₂ 1, 72 _3, ... includes two resistance wire 76,78a which are independent, even-numbered water cooled resistor ₇₂ 2, 72 _4, ... contains one resistance wire 78b. The resistance wire 76 constitutes the voltage dividing resistor 24, and the series connection of the two resistance wires 78a and 78b constitutes the snubber resistor 28.

In the thyristor valve 8X, heat sinks 62 _{1 to} 62 _{N + 1} are arranged on both sides of the thyristor 20 _{1 to} 20 _N , as in the embodiment of FIG. The heat sink _{62 1 ~62 N +} 1 of the water inlet is connected through a branch pipe to the cooling water inlet side header pipe 68, the heat sink _{62 1 ~62 N +} 1 of the water outlet is connected to a water cooled resistor _{72 1 ~72 N +} 1 of the water inlet To. The water outlets of the water cooling resistors 72 _{1 to} 72 _{N + 1} are connected to the cooling water outlet side mother pipe 70 via a branch pipe. Not all water-cooled resistors 72 have the same resistance value, but every other one has a different resistance value. Numbered water cooled resistor ₇₂ 2, 72 _4, ... includes two resistance wire 76,78a which are independent, odd water cooled resistor ₇₂ 3, 72 _5, ... contains one resistance wire 78b. The resistance wire 76 constitutes the voltage dividing resistor 24, and the series connection of the two resistance wires 78a and 78b constitutes the snubber resistor 28. Since the number of cooling paths is one more than the number of silis, one of the first and last water-cooled resistors 72 ₁ and 72 _{N + 1} should be used to balance the flow path with and without the water-cooled resistor. Includes dummy resistance wire 80. In this way, the series connection of the heat sinks 62 _{1 to} 62 _{N + 1} and the water cooling resistors 72 _{1 to} 72 _{N + 1} is arranged in parallel between the cooling water inlet side master pipe 68 and the cooling water outlet side master pipe 70.

In the case of FIG. 6, the cooling water supplied from the cooling water inlet side mother pipe 68 is injected in parallel to the heat sinks 62 _{1 to} 62 _{N + 1} , the water cooling resistors 64 ₁ to 64 _N , and 66 ₁ to 66 _N. in the case of FIG. 7, not cooling water supplied from the cooling water inlet side header pipe 68 is directly injected into the water-cooled resistor _{64 1 ~64 N + 1, 66} 1 ~66 N + 1, the water temperature at the heat sink ₆₂ 1 _{through 62 N +} within ₁ The increased cooling water is injected into the water cooling resistors 64 ₁ to 64 _{N + 1} , 66 _{1 to} 66 _{N + 1} . Therefore, when calculating the resistance wire temperature of the snubber resistor 28 and the voltage dividing resistor 24, it is necessary to consider the increase in the temperature of the cooling water.

In the second embodiment, the calculation unit 14a calculates the water temperature increase ΔT in the heat sinks 62 _{1 to} 62 _{N + 1} , and corrects the equation (9) using the result to calculate the resistance wire temperature.

The amount of increase in the temperature of the cooling water ΔT is calculated by the following formula.

ΔT = P / (ρ × c × Q) (13)
P is the calorific value, Q is the flow rate of the cooling water (L / min), ρ is the density of the cooling water (kg / m), and c is the specific heat of the cooling water (kJ / (kg · K)). The element loss _Pthy is used as the calorific value. The flow rate Q of the cooling water is detected by the sensor group 12, and the density ρ of the cooling water and the specific heat c of the cooling water are known.

The calculation unit 14a replaces the water entry temperature _{Trin in the} equation (9) with _Trin + ΔT, and calculates the resistance line temperature of the snubber resistor 28 and the voltage dividing resistor 24. The calculation unit 14a calculates the element junction temperature of the thyristors 20 and 21 by the equation (1) as in the case of FIG.
In FIG. 7, when the heat sink and the water-cooled resistor are connected in series, the heat sink is connected to the cooling water inlet side mother pipe 68, and the cooling water via the heat sink is injected into the water-cooled resistor. The connection may be reversed. That is, the water cooling resistor may be connected to the cooling water inlet side mother pipe 68, and the cooling water via the water cooling resistor may be injected into the heat sink.

In this case, calculation unit 14a, as the heating value by using the loss P _r generated in the resistance wire (13) the temperature rise ΔT of the cooling water calculated by formula, the incoming water temperature T _tin of (1) T The element coupling temperature of the thyristor 20 is calculated by substituting _tin + ΔT. The calculation unit 14a calculates the resistance line temperature of the snubber resistor 28 and the voltage dividing resistor 24 by the equation (9) as in the case of FIG. The second embodiment shows an example of a cooling pipe in which a series connection consisting of one heat sink and one water cooling resistor is connected in parallel, but the example of the pipe is arbitrary. For example, a heat sink, a heat sink, a water-cooled resistor, and a water-cooled resistor may be connected in series from the cooling water inlet side mother pipe 68. In either case, the element junction temperature and the resistance wire temperature can be calculated by calculating the temperature rise in Eq. (13) and correcting the water entry temperature in Eq. (1) or (9) based on the calculation.
As a result, as shown in FIG. 7, even if the cooling water is not injected into the heat sink and the water cooling resistor all at once and the temperature of the cooling water rises due to the heat sink or the water cooling resistor, the equations (1) and (9) are used. , The element junction temperature or the resistance wire temperature can be calculated correctly. According to the above-described embodiment, the element junction temperature of the thyristor and the resistance wire temperature of the resistor can be estimated by performing the calculation using the equations (1) and (9). Further, by monitoring the element junction temperature and the resistance wire temperature of the thyristor and controlling the operation of the thyristor valve, damage to the thyristor and the resistor can be prevented. Further, even in a cooling pipe configuration in which a heat sink and a water-cooled resistor are connected in series, the amount of increase in the temperature of the cooling water is calculated by Eq. (13), and the result is used to determine the element junction temperature of the thyristor. And the temperature of the resistance wire can be calculated.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

6 ... power converter, 8 ... reactive power compensator, 10 ... gate control device, 12 ... sensor group, 14 ... control panel, 20, 21 ... thyristor, 22 ... snubber circuit, 24 ... voltage dividing resistor, 26 ... voltage detection Vessel, 28 ... snubber resistor, 30 ... capacitor, 62 ... heat sink, 64, 66, 72 ... water-cooled resistor.

Claims (4)

Reactive power compensator with multiple thyristor valves,
Sensor means for detecting state data indicating the operating state of the reactive power compensator, and
A power conversion device comprising: a control means that calculates a temperature based on the output of the sensor means and controls the reactive power compensator according to the calculated temperature.
The thyristor valve is
With multiple thyristors connected in series,
A plurality of snubber resistors connected in parallel to each of the plurality of thyristors,
It is provided with a plurality of voltage dividing resistors connected in parallel to each of the plurality of thyristors.
The control means calculates the element junction temperature of the plurality of thyristors, the resistance wire temperature of the plurality of snubber resistors, and the resistance wire temperature of the plurality of voltage dividing resistors .
A plurality of heat sinks for cooling the plurality of thyristors,
A plurality of snubber resistors and a plurality of water-cooled resistors constituting the plurality of voltage dividing resistors are further provided.
The control means
Based on the thermal resistance of the plurality of thyristors, the thermal resistance of the plurality of heat sinks, the element loss of the plurality of thyristors, and the inlet temperature of the cooling water injected into the plurality of heat sinks, the plurality of thyristors of the plurality of thyristors. Calculate the element junction temperature and
Based on the thermal resistance of the plurality of snubber resistors, the loss caused by the plurality of snubber resistors, and the inlet temperature of the cooling water injected into the plurality of water cooling resistors constituting the plurality of snubber resistors, the plurality of snubber resistors. Calculate the resistance wire temperature of the snubber resistor,
Based on the thermal resistance of the plurality of voltage dividing resistors, the loss caused by the plurality of voltage dividing resistors, and the inlet temperature of the cooling water injected into the plurality of water cooling resistors constituting the plurality of voltage dividing resistors. Calculate the resistance wire temperature of the plurality of voltage dividing resistors,
Each of the plurality of snubber resistors is divided into a first resistor and a second resistor.
The plurality of water-cooled resistors include a plurality of first water-cooled resistors constituting the plurality of voltage dividing resistors and the first resistance of the plurality of snubber resistors, and a plurality of plurality of second resistors of the plurality of snubber resistors. Equipped with a second water-cooled resistor,
Each of the plurality of thyristor valves includes the plurality of first water-cooled resistors, the plurality of second water-cooled resistors, and the plurality of heat sinks.
The plurality of heat sinks are connected in series with the plurality of first water cooling resistors or the plurality of second water cooling resistors.
A series circuit of the plurality of heat sinks and the plurality of first water-cooled resistors or the plurality of second water-cooled resistors is arranged in parallel between the inlet side end portion of the cooling water and the outlet side end portion of the cooling water. Power converter to be placed . The power conversion device according to claim 1 , wherein the cooling water discharged from the plurality of heat sinks is injected into the plurality of first water cooling resistors or the plurality of second water cooling resistors. The power conversion device according to claim 1 , wherein the cooling water discharged from the plurality of first water cooling resistors or the plurality of second water cooling resistors is injected into the plurality of heat sinks. The control means is a reactive power compensator when at least one of the element junction temperature of the plurality of thyristors, the resistance wire temperature of the plurality of snubber resistors, and the resistance wire temperature of the plurality of voltage dividing resistors is equal to or higher than a threshold value. The power conversion device according to any one of claims 1 to 3, wherein the power conversion device is stopped or operated with a low load.

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